I played with a Windows Phone at the Verizon store for about an hour as I was there to upgrade my wife's iPhone from a 4s to a 5s. I was looking at phones for myself; I also have an iPhone 4s, and while it's not on its last legs, I like to know what my next move will be, should my phone be stolen or dunked or whatever. I played with all of them. Androids, BlackBerrys, Windows Phones, and iPhones.
I have a mostly dim opinion of the Android OS. Not because of any perceived privacy issue, but because of software bugs and glitches. They've been a part of every Android phone I've ever used or ever observed being used. The interface, while better than what it used to be, is still a pretty "dark" place to be. Most Android phones, technically, are pretty good; but I think the OS is rather poor.
I have to admit that I liked the BlackBerry the most of any of them, which is not what I expected. The on-screen keyboard was excellent and the interface was pretty good. I think I was using a Z10. Response was snappy and it felt like a quality piece.
I wanted to like the Windows phones. I really wanted to like them. I have an Outlook.com email account and I have files on OneDrive, and I thought that a Windows phone would integrate that stuff well. And it probably does. I couldn't get past the interface. The flat, tiled interface. It looked so...I don't know...
sterile. Apple's iOS looks "clean" to me...Microsoft somehow went beyond that and created an interface that's not particularly inviting to use. I'm sure one could get used to it. The Windows phones, on their own, are works of art. They have excellent cameras and excellent build quality. If you like the interface, you'll probably like the phones.
All that said, I'll probably get another iPhone. I use a lot of apps on my phone, but I play no games. I don't have any social media accounts. I have a lot of financial apps, I have a number of mapping/GPS apps, I have a few exercise-tracking apps, and I have a lot of news apps. The thing that I like about iOS is its popularity...and by that, I mean that no matter what type of app I'm looking for...if there's an app for something, there will be an iOS version of it out there. Android is prolific enough where you can usually get an app for that system. BB and WP are more hit-and-miss.
Just as an example, I invest heavily with Vanguard. They don't offer a BB or a WP app:
https://investor.vanguard.com/what-we-offer/account-services/mobile-services
My company's 401(k) program is with Fidelity NetBenefits. No BB or WP app:
https://401k.fidelity.com/public/content/401k/Home/Mobile
Our very prominent local news station offers iOS and Android apps:
http://www.wral.com/wral-tv/page/5787234/
Mapmyrun, perhaps one of the best spatial-tracking apps available, does not offer a WP app:
http://www.mapmyrun.com/app/
If you are one to not use apps beyond basic internet and email, any of the platforms are probably fine. If you use a lot of apps, even outside of the social media and game world, you may want to ensure that the apps that you do want to use are available on a BB or WP before you go that route.