Well, I'm 16 and have owned 2 BB, 2 Androids, 2 iPhones and 1 WP in the last year and a half.
Lets review them!
Blackberry: in love when I first got it. In 2011. It lasted until late 2012 (I think) when I got a touch screen bold because the curve broke. I loved the bold. Except I wasn't a huge fan of the AppWorld as it didn't have many fun games or apps.
Android: I wasn't a huge fan of the layout, but I did love the PlayStore because, well, it was much better than AppWorld. I also loved having a whole touchscreen with no keyboard. That was fun! Though I owned a LG Cookie when I was younger so I had a touch screen phone before.
iPhone: wow! It was everything I imagined and more. Loved it. Still do. Apple is amazing. Though I did eventually get bored of the layout. The AppStore is great! Though I notice too many people had them which made them look totally unoriginal! I still love iPhones.
WP: love the design and layout. Though I think the store is very small. Hopefully it'll expand.
All in all I prefer the iPhone and the Windows Phone. I'm not too keen on the Androids though I know a ton of people who are in love with them.
Oh, and I despise blackberrys. They're terrible boring phones! I will never buy one again. Next time I get a phone it'll be either an iPhone or WP… Possibly an android but I'm not too sure yet.
But that's just my opinion. What's yours?