I just got iphone 4, the antenna issue isn't a big deal. I've heard if you get a case though, you won't have the problem. But honestly, holding the way you have to, isn't a big drag. I'll admit, its a bit annoying, but you just get used to it. Its like switching from and ipod touch which has the power button on the top left, to the iphone 4 which has the power button on the top right. Also, call quality is great, even with 1 bar, and traveling at 30mph+ in a car.
If the voice control had more functions it would be better then Android's voice. I've used a Motorola Droid, the voice control is awesome. However, you can get the Bing app(FREE!) for iPhone which allows for voice search. Theres also an app, "Dragon Dictation" which allows voice to text input, although you have to copy and paste it to use in other apps.
Personally I liked Safari better than Android's browser. I also found that having a home button is a lot better than having a home, back, search, and option/menu button at the bottom of the device. On the droid, the buttons were sort of in the way if you using the phone one handed and were tapping w/ your thumb.
I have tried syncing Android w/ a computer, but seeing the youtube videos, I would say that iTunes has much better control, ease of use, 1-click syncing.
I liked the iPhone's digital keyboard more than Android, they are slightly different and I don't like physical keyboards. But if your a physical keyboard fan, that would be a major downside of the iPhone.
In terms of Verizon vs AT&T, I've had NO problems with AT&T.