Funny how the iPhone suddenly has a "small screen"... When it first came out the phone and screen were criticized for being impractical due to it's large size.
http://dl.dropbox.com/u/6857506/3.5in.png
Purple is the Galaxy SII circle. Orange is the iPhone circle.
Apparently the iPhone gives you magically larger hands for your smaller device. The confirmation bias is so thick it hurts.
I don't see any advantage to having a bigger screen. Especially when the bigger screen has less pixels (i.e. Galaxy S II). In that case, you actually have less pixel space for UI elements, text, video, etc. than you would with the smaller, denser screen.
Reaching and comfortably reaching are different.
I looked into the Galaxy Pro (http://www.gsmarena.com/samsung_galaxy_pro_b7510-3850.php) , but it looks like a bad compromise.
Seems to me that it's all about the difference in size. A full-sized physical keyboard is well superior to a virtual one. But on a tiny phone, either way is going to be painful, so it matters much less.