You (OP) said nothing about price......therefore the 70-200/2.8II IS is the one, no question. If you can, just get it. If you have to stretch or wait a little while, it's worth it. If it's out of the question for now and you don't want to miss shots, there are a number of very good compromises, sort through the ones recommended in the responses. Can't go wrong with an L prime if that's the choice.