first, you're a bb user
did you like the sparse bb marketplace? (i have access to droid/ios/bb)
and you want better?
better would be droid
best would be ios but it usually goes like this for dev schedule.
"we're releasing our ios app today, look for our droid app next month"
i have no idea on windows app. but i would assume they suck, just like droid sucked for 2 years (they are now just catching up to ios)
hardware... imo, as long as the cpu is dual core, it doesn't matter really, and all smartphones will be dual or even quad core, now if you use the phone for videos/pictures you might want to consider the more picturey phones like gs3 ip5, they both use the sony camera.
of course hardware means screen size, take your pick, you come from a micro screen, anything would be an upgrade, imo the gs3 size is perfect, and the ip5 is playing catch up
typing
you have the best smartphone input, now your gonna use screen input, ip5 tap tap tap sucks, when compared to recent advances such as swype (google it), for me swype (droid only) replaced the need for a hardware keyboard input.
i have a gs3, wife has a ip4 and work is allowing her to replace her bb with an ip5 (next week) different devices for different ppl.