I think they are the second best thieves because I, well, ummm, didn't think hard enough

. I'd completely forgotten about the DEX modifier and was going on racial adjustments. So, they're actually the worst thieves, as they lose the 25 bonus points for 18 (later 19) DEX.
Still, I do think they make the best thieves and F/Ts, if only because you can usually get enough skill points to do most of what you want whatever you choose.