Canon 100-400 vs 70-200 with a 2X Teleconverter

Which is better? If you get the 70-200 f/2.8 L IS II lens (http://sdp.io/c200) and add the Canon 2X III teleconverter (http://amzn.to/1KkeKTz), you'll be able to use the 70-200 at f/2.8 when you need to and two stops more light (and background blur) in that range than you can with the 100-400 II (http://sdp.io/c100400). When you need the extra reach, you can add the teleconverter and jump to 140-400mm f/5.6.

The total cost is pretty similar, so which is better? Will the teleconverter make the 70-200 noticeably less sharp at 400mm?


Text and video via Tony Northrup