If one were to buy a non-Canon 70-200 F/2.8 which one would you get? Sigma or Tamron? I have seen some reviews on the Sigma but not so many on the Tamron. I have heard good things about Tamron and Sigma with their NEWER lenses. Which one would you get? I think it may be worth the savings to get some portraits and shots of indoor sports events and concerts. I would be using a 7D at high (1600) ISO for a lot of the use of the lens.