Well as everyone else stated, its all personal opinion and your experiences with the phone.
I like iPhone's in general. I really enjoyed my 3GS so i moved on to the 4s. One reason being i have quite a few accessories that I've purchased that work very well, and have a 30 pin dock, so won't work with other phones. Lots of people like to say "wow what a waste, what if you don't have an iPhone anymore". To be honest, if i for some reason switch to android, i would just keep the 4s i have now and use it as an iPod so i will still be able to use my accessories. No Biggie there.
Also I know many people at work and just friends who have an android, and on average i'd say about 75% of them complain about having to restart their phone at least once a day. Now i'm not saying this is a widespread problem, but from my personal experience, that's what I've seen and its annoying, and i wouldn't want to deal with it. Just yesterday a co-worker was trying to show me something and his phone just decided to reboot on its own.
Also i really like the layout of iTunes, and how i can organize my music. I've been using it since i got my first 1GB iPod nano as a high school graduation present, and i just can't seem to walk away from it.