« on: November 13, 2014, 03:31:20 PM »
Depends on whether or not you'd use it as a walkaround setup. I started with the 70-200 II and got both TCs for it, but in the end, I preferred getting a 70-300L for zoos and as a lighter travel solution because the 70-200 II with TCs is harder to handle and carry on a strap. I see the 100-400 II in roughly the same vein. I like the pics from the 70-200 better than the 70-300L, but I prefer the portability of the 70-300L more in these situations.
I had a similar situation at the other end of the focal length spectrum. I had a 16-35 f/2.8 II but I never liked it. So, I bought a bunch of primes and the 16-35 II was left unused. Then the 16-35 f/4 IS came out, and I swapped the f/2.8 II for it, and now I use the 16-35 f/4 a lot.