TriX wrote:
If you mean indoor performances and conferences, you may find either combination slow in terms of minimum f-stop. If you can afford it, consider the 70-200 f2.8L. You'll appreciate the extra speed, and I can attest that it works well with the canon 1.4EX extender. It's not a light lens, but it's a workhorse that you find in many pro's bags. I use mine for everything from portraits to weddings to indoor sports, but when it comes to wildlife, outdoor sports, or BIF, I reach for the 100-400...
I would LOVE to own the 70 to 200 2.8. I've shot with that lens before, and it is wonderful. Lovely bokeh. It's out of my budget unfortunately. While I will use whatever I end up with on my 5DII now and then, the primary use will be actually be on a C100 video camera. You can shoot at very high ISO with minimal noise with this thing. Used my 24 to 105 F4L many times covering stage performances, and it is definitely fast enough.