The open nature of Android certainly has advantages over the iphone, but Apple secured a pretty hefty first-mover advantage. Also, they got it right from the start (or V2) with a great design, whereas Android still feels very much in alpha.
Background processes are a big win and would be a huge factor for me, but I'd need to see some improvement of handset design before I'm ready to switch.
The real question is when will we see a more polished Android phone?