What specific reasons?
The phone feels dated, to be completely honest. After having the SII for a week and then picking up her phone when she got it, I felt like I was picking up my old 3G. The UI is the same as it's always been and it feels clunky after using the sleeker UI of the SII. It took me a while to remember that I had to back out of each application in order to do something else. I pulled down the notification bar and thought it was pretty cool, but then I clicked on something and wanted to get back to where I was and thought "well how do I get back" and then realized I had to back out of the app I was in and go back to the homescreen and reenter the app I was already in. It felt like a huge step back, to be honest. And for all of the "it's intuitive and just works out of the box" crowd, I sat there for a good 5 minutes trying to figure out where to access iCloud and FaceTime, I had no idea.
Also, the phone is thicker and heavier than my SII, which was very noticeable. I know some people that say the 3.5" screen is the sweet spot, but it felt weird going back to a screen that small and having the huge spaces between the edge of the phone and the edge of the screen itself.
After we hopped in the car from getting it, I played with it for a bit then handed it back to her and said "I'm glad I didn't get that phone". To each their own, it's a comfort thing for her, but I'd be missing out on a lot of cool stuff if I had just blindly gone with the next iteration of the iPhone instead of being open minded about it.
EDIT: I'll also add that after using the capacitive buttons on the SII, the physical button on the iPhone feels cheap and unnecessary.
EDIT2: I'll also add the caveat that the SII felt very 'new' to me, like a new toy, because it was totally different than the iPhone in a lot of regards, so that process was fun for me, which may be coloring my view a bit. When I picked up her new iPhone 4S, it felt same as old, but newer if that makes sense, so it was a bit underwhelming compared to my experience getting a phone that I had to explore again.
Edited by FL4WL3SS, 14 October 2011 - 10:14 AM.