The newest Tamron 70-200 2.8 G2 is getting amazing reviews and many are calling it the best value 70-200 on the market. It's made well and produces results that are, in my opinion, equal to or better than the OEM equivalents.
I have the previous version of the Tamron (70-200 2.8 VC) and absolutely love it.
I say buy the Tamron and you won't regret it. If you wanna dump an extra $600 on a lens just to get a white one with the canon name on it, go ahead. But I wouldn't.