Very good comments here. My own experience is that I've shot with the 70-200mm f/4L IS USM, 70-200mm f/2.8L IS II USM, and the 70-300 f/4.5-5.6 DO IS USM. The 70-300 does not work well for fast moving objects because its aperture is too small. The 70-200 variants are much better in this regard, and are orders of magnitude sharper. I found the f/4L version to not accurately reproduce color. Blues looked very artificial with it. I opted for the f/2.8L II version despite the heavier weight (and price tag). It reproduces color very accurately and is truly top of the line in every way. I use it with a tripod a lot however, and in those situations the IS isn't important (although it does help when shooting video at 400mm with a 2X extender). If you are shooting handheld, you will definitely want IS, although like others said it will not prevent subject blur.
Alternatively you may want to consider the 135mm f/2L USM. It would be able to stop subjects better than any f/2.8L, although it may not be enough focal length for your needs.
The-Digital-Picture.com has really detailed reviews for all of these lenses btw.
Alternatively you may want to consider the 135mm f/2L USM. It would be able to stop subjects better than any f/2.8L, although it may not be enough focal length for your needs.
The-Digital-Picture.com has really detailed reviews for all of these lenses btw.