I prefer Android lately, I have the EVO rooted with CM 6.1 and it is pretty darn cool. But my Brother currently has a 2yr old iPhone3G, and it is flaky and running like poo lately, he wants a new phone this week. I told him about the Nexus-S, and he is not to sure about going Android yet.
He said there are some cool features with a jailbroke iPhone 4 ? He likes the thinness of the new iPhone and great battery life, plus the screen res is amazing. To me the screen is too small for a cool smart phone, and no widgets blows, but that's what jailbreaking is for I guess.