Screen size seems to pull many people from iPhone. I find larger displays uncomfortable though (heavily using one handed) but it seems that people want that.
Kinda off topic, but what's the email client situation on Android? I don't use Gmail and the last time I used Android (ICS I guess), mail clients were from stone age.
No idea but I'm not too picky. As long as I can read it and search it I'm fine, so I just use the standard Gmail app. I like the larger screen because I want to have one device with all my music on it, with the ability to read on the commute.