Here's what I want you to do. Buy the cheapest windows pre-paid phone you can buy. I would suggest something like
Blu Win HD or something else with a nice 5 inch screen like
lumia 535. These phones are dirt cheap even unlocked. Locked down probably cheaper. Once you get it, get the "developers preview" app. Not the Windows insider app. Install the latest phone updates. Use it for a while and see if you like it. That's the only way you will know.
My brother abandoned Android after he used Windows for a bit. A lot of people do love the UI when I let them play around with my lumia 830. This will give you time to find apps that you need to function. There is an app issue but there are lots of third party apps that replace some of the popular ones that are missing. With that said, since I have been using this phone the app gap has been slowly closing. Windows 10 will probably make that even less of a problem. People generally do prefer the Windows UI. That is what makes windows, no doubt about it. The level of customization and creativity lets people really enjoy their phone.
Stick with the cheap phone until some of the better phones start coming out near winter time. You may even find that it's enough for you.
I have all 3 platforms. Yes, iphone is great for apps no doubt. Android is kind of a mess if you ask me, but it does what you need it to do. I think Lollipop is a decent iteration of android but it's still not a final solution. Android M is supposed to help even more with speed issues and all the problems it comes with.
If you find you don't like it, just keep it in great condition and sell it. You may lose a bit of money but think of it as "renting" to test. People can tell you this or that but really you need to test it yourself. I think Windows is more tailored to the individual hence all the customization.
Security wise, so far Windows is the better one out of all of them but that could change in the future once it's more popular. Keep in mind that Microsoft has included malware/virus detection in their windows platform for a while. They have learned a lot about how malware/viruses work and have built a platform to try to protect against that. Windows 10 is supposed to be quite secure. Also keep in mind that Windows 10 is built around the users. People helped shape the OS. And they will continue to shape it because Microsoft is listening. IOS releases an update, you are stuck with what is changed and don't have any say. Windows 10 is going to focus more on options. You don't like this, turn it off, someone else may like it they keep it on.
I have a Lumia 830 and I LOVE IT!
The screen is great, I love customizing my start screen to suit my needs and show off my artistic side.
The camera is insane. I have had point and shoot cameras that are not as good as this. People will comment on how good the camera is when I show them pictures. And the design of the lens isn't bulky in the least bit.
This is how my UI looks. It's individually tailored, no one will have that same UI. Well unless they copy it hehe.