I know I keep bringing this thread up, and yes as I promised I will write a proper review/comparison and start a new thread, but I am having so much fun with this lens that I don't find the time to do that (yet)!
I just tried the 1.4x and 2.0x extenders today (Mk3) and I have to say that 2.0 is very impressive. 1.4 is obviously a lot sharper, but it just gives me 280, not so much of a difference. With 2.0, I get 400mm and the focus is much faster than I expected (I wouldn't even be able to say that I have an extender on). It tracks on AI Servo quite well and interestingly enough, I get very decent shots wide open F4 and much sharper stepping it down to F5.6. I was a bit disappointed though to find out you cannot stack the MK3 extenders, but even still, I think 2.0x is my next purchase.
That being said, here is the first comparison shot between the zoom and the prime. I am going to do a lot more of these, but this should give you guys an idea. Warning though, people with the zoom is not going to feel better after seeing this!
I have other shots where I stopped the prime down to 2.8 and the difference is even more obvious there.
200L @ 2.0 vs 70-200 IS II @ F2.8
The 70-200 II is widely known as the sharpest zoom lens available from any company. Every review I have ever seen has praised this lens. Looking at crops from The Digital Pcture, the IQ differences between the 70-200 II at 200mm and the 200 2.0 are subtle.
If you are legitimately getting results like shown above, you obviously have a defective lens and should have returned it immediately. But honestly, considering the quote I highlighted above, it seems more and more that your just trolling on these forums or at least trying to create more drama.