I'll probably want a duel core phone in a few years when HTC comes out with one. I don't see much advantage getting one now.
However, of the Bionic was also released next week, I may rethink that.
The iPhone has a great browser and good app selection. But I don't like how it handles notifications or customizations. My parents have one and it's great for them because it's easy to use.
You won't have to wait years for an HTC dual core. The Pyramid is coming out this summer for T-Mobile (yuck) and will be dual core. Also, from everything I've read the Bionic won't be available until June/July. Moto probably doesn't want it competing with the Atrix.