Steel is stronger than aluminum - no arguement there. I do take some issue with the idea that aluminum is stronger than carbon. It depends greatly on how each product is make. Carbon will probably cost you a little more, but there are some OK carbon forks out there that aren't too expensive. I am not into tricks at all, so I can't really help you out with product reviews there, but I would guess that for materials, steel is best, carbon is next, and aluminum is last. Really, I can't think of a worse material to make a fork out of than alumium (OK, that's not true, but you get the idea). I would stay away.

Also, you cannot powdercoat carbon. Sorry for being suck a buzzkill.

FYI, here is some gearing info:
52x17=80 gi
43x15=75 gi
43x17=66 gi
43x18=63 gi
38x16=62 gi

Just FYI