i have an iphone and am an iphone app developer.
from my personal experience i know 5dimes.tv works fine on the iphone. the iphone app market simply blows the android market away, my roommate has one and we trade and compare sometimes. the android wins out in integration with google, so if you use google docs or want google maps to have turn by turn directions, android is the way to go.
however, wait till the next iphone which should be in july. the iphone generation 4 will be another great improvement. i dont wanna get into technical reasons this late but they are making it so apps can semi-run at the same time together in the background, as well as finally getting turn by turn directions. also, the next iphone may have video conferencing and an improved camera (see leaked iphone articles).
obviously im kind of a fan of my iphone, but i would definitely recommend waiting till the next iphone is released soon, and then comparing it to the latest-released android based phone.
figured id throw in a shameless plug here as well, search for live odds on the app store and look for the one with the red sp logo...