Apparently you haven't read any of the numerous articles on Google's play store about it being plagued with apps having malware. Yes it is a problem, yes being popular will draw more malware writers, and yes it is targeted as well because they are lax in security and more open as an os for malware issues.
I obviously have, apps with malware have also appeared on iOS. You don't understand do you? If you stick to using mainstream apps developed by reputable developers you won't find malware.
It's common sense really. Windows has a lot of viruses, I've been using mine since last year and thank God it's been fine.
The best anti-virus is common sense, and it's free.
If I was to choose an os for customization and power it would be Symbian as it is way more customizable and able to do thing no other os can to this day. Android defitly has its perks they all do, it depends what the user wants and prefer. I like the simplicity and smoothness of WP. I hate widgets and android is too fragmented for me, can't stand apple, but I can understand why people use each one. There is no best os it just depends on peoples preferences.
Your last point is wrong. Measuring the advantages and disadvantages of an operating system you can decide which operating system is best.
Most reviewers can't decide between whether iOS or Android is best and that is where preferences play a role.
Windows Phone still lacks so much functionality that no one in their right mind would say that it is the best OS, no matter what your preferences.
Ok I've used a SG1 and SG3, bought Nexus 5 from Google, upgraded from SG3 contract to a now Xperia Z2. But before that upgrade got myself a used Lumia 920 out of curiosity, sold that recently and bought a 930 and a 1520 (why have a tablet when you can have both!) Have also used iPhone as my partner has a 4 and 5c. With my experience it was Windows phone that gave me the best experience and fun with reliability of all phones used - a personal choice! I still use my Z2, but still
not as smooth or elegant or crash/glitch free compared to both iOS and W8.1. I still stick with my points against Nexus 5 viewing angle losses colour and fades when not looking directly at it, and under sunlight it suffers. Battery was weak on Nexus. It still had glitches - I found sometimes you zoom in the screen gets stuck, apps did freeze at times, and the usual android problems as still occur on XZ2. For evidence my buddy who has a red Nexus 5 comes to me with annoyance of android as I'm quiet aware of them having been with Android since the original SG1 release and still am, though I use and trust my Lumia 930 more. You can also see my reviews of XPZ2, Nexus, and Lumia phones putting out the reality of the phones on Amazon UK. So I'm not a fan boy, I just use the best phone for results, ease, functionality for real life - which I find iPhone(don't use it myself) and W8P do a better and reliable job of.
No operating system is perfect and I've seen apps crash on iOS, Windows Phone and Android.
I've owned a Nexus 5 since the past month and yes I have seen one app in particular that crashed a few times, it's called Amateur Surgeon 3. Considering that the app isn't even on the Windows Phone Store so it doesn't matter. Plus the app hasn't crashed after having downloading the data.
Android has matured into a very stable and beautiful operating system and I would like you to point out what apps are crashing on your device?
Plus I find scrolling and multitasking a lot better on Android, I can scroll much faster depending on how I press the screen and multitasking is instant, no more waiting for the "resuming" screen.
In the end you go onto mension that you like functionality and ease of use, ease of use is debatable but Android hands down has more functionality in most, if not all apps.