One BIG BIG reason I love my EVO and Android in general--customizability.
Seriously, as great as the iPhones are, and they are technological wonders, one can't customize them as much as with an Android phone. So far, I've been able to root my EVO, partition its 16GB SD card, and put Myn's ROM on it and do things I'd never be able to do with an iPhone.
Oh, plus its largest screen in its class helps this >40-year-old with his reading ability. Yes, I've enlarged the fonts, but that can only go so far.