I'd get the tamron, The original 24-70 is a good lens but a bit long in the tooth. The tamron is better in every way except built quality, Plus VC.+1
Unless you have the budget for the MK2, the tamron is the obvious choice.
If I didn't have my Canon 24-70mm MK1, I would get Tamron 24-70mm VC now. Many reviews say Tamron 24-70mm overall is better than Canon 24-70mm MK1. For wedding Canon 24-70mm MK2 may be the best; however, it's not out yet.
-0.5 is about Canon 24-70 Mk II. It has no VC. And there are plenty of situations in which one needs VC at weddings. I rather preffer not to use flash for many reasons - one of the most important being that the people must be natural in order to get "the shot" and the flashes of the flash break the intimate atmosphere of a wedding.
+1 also for 50mm primes.