For the rain/commuter/beater/2d bike, go with a cheapo carbon frame. It will be better, smoother, lighter, more comfortable, and you'll ride it more.

This is a pic of my 2006 BMC in my office today. I rode it in the rain this weekend, and now I've rode it to work. The frame had a crack, and it was repaired by Calfee (repair work at headtube), and so I don't worry about beating some expensive frame. I have a triple, as I use it for doing very steep climbs. So, this is the all-purpose, do-everything bike. The components had been on an aluminum framed bike, and I enjoy this a lot more.