Steel is the best for getting away with stuff and it would be fun to fall upwards.
Now, I've noticed Vin uses a lot of pewter for steel pushing and iron pulling, so therefore you need to have one to make the other one useful.
Its the same with being a seer, atuim lets you see what the other person is going to do, but you would probably want some pewter would you not?
These are just examples so lets cut the cheese
I will vote on steel because its just plain cool.
I just won't jump too high!!!