It was with a heavy heart that I went to my local ATT store and bought an iPhone 6. My 1520 had been on the fritz for months, and even after going to the MS store and having them take a look at it, it finally became unusable. Apps would spontaneously launch, the screen was unresponsive at least for half the day, and it would reboot in the middle of a call. There was nothing that was close to the 1520 that I wanted to waste a 2-year contract on. I figured, I'd still get a lot of MS apps over on iOS, and if I hated it then I could tough it out and hand it off to my wife when the Windows 10 phones arrive. This is my first iPhone, so I really did come into it blind. The only other operating system I had used before was Android, and I wasn't going back to that mess. So here is my purely anecdotal comparisons when my 1520 was at peak fighting shape:
Build:
This one is tough. The iPhone feels great in the hand. The edges are rounded perfectly and there is enough travel on the volume and power keys. My 1520's keys were always flush with the frame and it made manipulating them difficult at times. But, even though it feels well built, going from the 1520, it feels fragile. I hate putting covers on a device, but I got the bumper for this because I felt like I had to. It is light as a feather, and this may be why I think it could crack like an egg.
The 1520 is harder to hold, because it is ridiculously bigger and the edges dig into your finger. It squared off in every way and feels like a slab of marble, but I never once felt the need to put a case on it. If it fell off the bed, I didn't blink. It has a warm feeling compared to the coldness of the iPhone. I thought once I went big, there is no going back, but I like having room in my pocket, and being able to bend my legs. I don't wear skinny jeans and I'm 5'10 and 150, so pretty average. However, I always knew the 1520 was there, the iPhone, I can kind of forget about it for a while.
Screen
Not even close. the 1520's color, vibrancy, feel, etc. is better in every way and I am reminded of this every time I power on the iPhone. Scrolling is easier on the 1520 as well.
Speaker
This one goes to the iPhone. It sounds clearer, cleaner and louder.
Camera
For good enough to great enough fast shots, iPhone wins. Even with the dedicated camera button, which I miss and should be standard on every phone, I can still get the iPhone up and out faster than the 1520. If you take a lot of photos in the auto-mode then the iPhone does a better job giving you a consistent shot. As far as photo quality goes, the iPhone algorithm makes shots look vibrant, but as far pas post-editing, I could do so much more with the 1520. Night shots are also a big advantage for the 1520. The iPhone is decent at Night, but not great or rarely good.
Battery Life
1520 easily. I really had to download a bunch of crap or use GPS for me to need to reach for my charger nightly. IPhone 6 I need to charge it nightly. It'll get me through 18 hours, but come midnight, the battery is looking more like a pumpkin than a carriage.
Operating system basics
IOS is a "whack-a-mole approach to apps. I am constantly jumping in and out to get things done. The app switcher helps alleviate this some, and WP 8.1 is sadly heading into that direction. The biggest thing I miss on a daily basis is how WP deals with contacts. Having all their online profiles, email, pictures linked in the People hub is amazing, and when you go to iOS it feels like getting out a concrete address book. It is static, stale, and uninspiring. It makes you not want to contact people.
The only benefit of having a static grid of icons vs. live tiles, is I don't spend as much time staring at phone screen. Being able to tell what a quick message said or post without opening it is nice. Yes, I realize the toast notifications and drop down tray do this, but it is still a small step, but live tiles felt like a forward progression, and frankly they look a hell of a lot nicer. I also like scrolling down a list instead of across, but it could be what I a used too.
Touch ID works, and it works well. It, so far, has never missed a read. I miss tap to awake and the peek mode, but since touch id is so fluid it is a draw.
One thing that is glaring on iOS is the apps. Yes, you have everyone you can think of and want and not want, but they are littered with adds. WP's Facebook, Twitter, etc. never had any ads, at least I never noticed. I guess that is a benefit of 3% market share. Still, Nokia Here is available (and Google and Apple maps), as well as, MS Office suite, Bing, and One Drive. Ditto for Smartglass and Xbox music, which really doesn't seem that bad compared to the official version which I continually have problems with. No Xbox video though, and this is a bummer. Yup, all the "official" apps are here, and in many cases offer more functionality, but in a few they offer less (i.e. Metrotube). Additionally, accessing your phone via PC, well this one has to go to iOS. The WP phone app is horrible, clumsy, and since the update never, ever works. ITunes is pathetic, but at least it functions.
Siri vs Cortana
Siri sucks once you've dated Cortana. Cortana is charming, witty, and useful. If Cortana is Emma Stone, Siri is a Kardashian. Looks nice, but vapid and shallow. "Hey, Siri" only work if it is plugged in, and can be utilized as an app launcher for Xbox Music, anything else requires you to use iTunes. My wife mentioned she has never used Siri, and I can see why.
Overall
Do I love the iPhone like I did my 1520? No, but I've gotten used to it quickly and it is more than serviceable. If you need a basic phone that does bit more and you want a plug and play experience then the iPhone takes it. Almost everyone I know has an iPhone so Facetime is easier to get them to use than Skype. I no longer have to walk my wife through using my phone when she needs to operate it in the car, and I have my pocket back. Making actual phone calls is easier and more comfortable and most of the Windows apps I need or want are available. But every time I want a better virtual assistant, see a bit more, be wowed by the OS, I miss WP.
Build:
This one is tough. The iPhone feels great in the hand. The edges are rounded perfectly and there is enough travel on the volume and power keys. My 1520's keys were always flush with the frame and it made manipulating them difficult at times. But, even though it feels well built, going from the 1520, it feels fragile. I hate putting covers on a device, but I got the bumper for this because I felt like I had to. It is light as a feather, and this may be why I think it could crack like an egg.
The 1520 is harder to hold, because it is ridiculously bigger and the edges dig into your finger. It squared off in every way and feels like a slab of marble, but I never once felt the need to put a case on it. If it fell off the bed, I didn't blink. It has a warm feeling compared to the coldness of the iPhone. I thought once I went big, there is no going back, but I like having room in my pocket, and being able to bend my legs. I don't wear skinny jeans and I'm 5'10 and 150, so pretty average. However, I always knew the 1520 was there, the iPhone, I can kind of forget about it for a while.
Screen
Not even close. the 1520's color, vibrancy, feel, etc. is better in every way and I am reminded of this every time I power on the iPhone. Scrolling is easier on the 1520 as well.
Speaker
This one goes to the iPhone. It sounds clearer, cleaner and louder.
Camera
For good enough to great enough fast shots, iPhone wins. Even with the dedicated camera button, which I miss and should be standard on every phone, I can still get the iPhone up and out faster than the 1520. If you take a lot of photos in the auto-mode then the iPhone does a better job giving you a consistent shot. As far as photo quality goes, the iPhone algorithm makes shots look vibrant, but as far pas post-editing, I could do so much more with the 1520. Night shots are also a big advantage for the 1520. The iPhone is decent at Night, but not great or rarely good.
Battery Life
1520 easily. I really had to download a bunch of crap or use GPS for me to need to reach for my charger nightly. IPhone 6 I need to charge it nightly. It'll get me through 18 hours, but come midnight, the battery is looking more like a pumpkin than a carriage.
Operating system basics
IOS is a "whack-a-mole approach to apps. I am constantly jumping in and out to get things done. The app switcher helps alleviate this some, and WP 8.1 is sadly heading into that direction. The biggest thing I miss on a daily basis is how WP deals with contacts. Having all their online profiles, email, pictures linked in the People hub is amazing, and when you go to iOS it feels like getting out a concrete address book. It is static, stale, and uninspiring. It makes you not want to contact people.
The only benefit of having a static grid of icons vs. live tiles, is I don't spend as much time staring at phone screen. Being able to tell what a quick message said or post without opening it is nice. Yes, I realize the toast notifications and drop down tray do this, but it is still a small step, but live tiles felt like a forward progression, and frankly they look a hell of a lot nicer. I also like scrolling down a list instead of across, but it could be what I a used too.
Touch ID works, and it works well. It, so far, has never missed a read. I miss tap to awake and the peek mode, but since touch id is so fluid it is a draw.
One thing that is glaring on iOS is the apps. Yes, you have everyone you can think of and want and not want, but they are littered with adds. WP's Facebook, Twitter, etc. never had any ads, at least I never noticed. I guess that is a benefit of 3% market share. Still, Nokia Here is available (and Google and Apple maps), as well as, MS Office suite, Bing, and One Drive. Ditto for Smartglass and Xbox music, which really doesn't seem that bad compared to the official version which I continually have problems with. No Xbox video though, and this is a bummer. Yup, all the "official" apps are here, and in many cases offer more functionality, but in a few they offer less (i.e. Metrotube). Additionally, accessing your phone via PC, well this one has to go to iOS. The WP phone app is horrible, clumsy, and since the update never, ever works. ITunes is pathetic, but at least it functions.
Siri vs Cortana
Siri sucks once you've dated Cortana. Cortana is charming, witty, and useful. If Cortana is Emma Stone, Siri is a Kardashian. Looks nice, but vapid and shallow. "Hey, Siri" only work if it is plugged in, and can be utilized as an app launcher for Xbox Music, anything else requires you to use iTunes. My wife mentioned she has never used Siri, and I can see why.
Overall
Do I love the iPhone like I did my 1520? No, but I've gotten used to it quickly and it is more than serviceable. If you need a basic phone that does bit more and you want a plug and play experience then the iPhone takes it. Almost everyone I know has an iPhone so Facetime is easier to get them to use than Skype. I no longer have to walk my wife through using my phone when she needs to operate it in the car, and I have my pocket back. Making actual phone calls is easier and more comfortable and most of the Windows apps I need or want are available. But every time I want a better virtual assistant, see a bit more, be wowed by the OS, I miss WP.