iTrader, because it's much more relevant and shows you if a person is truly trustworthy from real experience or not. I don't pay too much attention to Rep, but I think both do play a role.
Although we are still relatively new here, this is how we see it: Both systems have the potential to be manipulated. I think the quality and the ability of some ones product is the biggest factor. If they are able to deliver a great product, then more power to them. We dont have respect for people on here that are openly advertising to sell rep or i trader points. They are manipulating a system that was designed to give accurate information on a user here. I think I would look at how they market, how they respond to inquiries, what their product(s) are, where they are located, and other factors.