I've been out of the WP game for a while but I personally left because of the App situation. That might have changed but games and apps didn't come out for Windows Phone, they came out for iOS and Android. Many popular apps (Instagram, for example) were still missing from the store. I just never thought of Windows Phone to be a good ecosystem.Why not a Lumia?
The OS is great, the speed is great, the integration of various services is great but if you're into apps, it's just not on par with Android or iOS.
OP should go with whatever he likes the most. You cannot go wrong with either but certain people will be more happy with Android than they'd ever be with iOS and vice versa. I like Android, the customisation possibilities, the fact that it's fast these days and that I can play with a DualShock. I really like the build quality of the iPhone 5, though. My girlfriend is really happy with her phone.
I get what people mean from a technical standpoint but I don't see any disadvantage and prefer it to the Vita's screen, for example.I'm as picky about resolution as the next guy and I really fail to see what the commotion is about the S3's screen, it's gorgeous.