70-200L vs 100-400L

It was a tough decision when it came time to purchase a lens that I was planning to use often at 400mm. After eliminating other third party lenses, it came down to a choice between the 70-200L f/2.8 with a 2x teleconverter or a 100-400L. The 70-200L had the advantage of being a fast useful lens when not on the teleconverter, but it was very heavy and as the results show, it lost out to the 100-400L in image quality at 400mm at identical settings.

Note that I still think the 70-200L f/2.8 is a fantastic lens, and operting it at 400mm was outside its design parameters. In light of this, it did extremely well, but the 100-400L was the correct choice for my requirements.