Canon 24-70mm f/2.8L II Vs.Tamron 24-70 VC

I am shooting a Canon 40D with a Tamron 17-50 (non VC) and I am looking to move up to a 6D within a few months and I have been reading review after review on both the Canon and Tamron's 24-70mm f2.8 lenses. Some are saying that the Tamron is sharper than the Canon and it is $1,000 cheaper. Do any of you have any experiences with both lenses? Any recommendations? I mostly shoot nightlife by the way.

Cheers!

I don't look only at sharpness. Color accuracy, the degree of micro contrast, and the bokeh are all important to me, sometimes more than simply sharpness.

Why? Because sharpness is most apparent on a 20 x 30 enlargement, and most of my prints are 8 x 10, and blur, contrast, and color come through a lot more on an 8 x 10 than small differences in sharpness will.

Just something for you to think about if all you're looking at is a sharpness differences.