Canon 600 f4 II vs Sigma 300-800 5.6 (vs 200-500 2.8)

[RacingSnake]

Does anyone have any real world comparisons of these 2 (3)?

I currently have the sigmonster, but find I have to close up the aperture (to 7.1/8.0) for maximum sharpness, and anything other than good sunlight drops the IQ significantly... I then open up the aperture to try to let more light in and the quality drops. - I also find myself 95% of the time at 800mm (so not really using the 'zoom' function so much).

Now I know a lot of this will also be down to the body (I'm currently using a 7d), but I plan on replacing this in 2016.

In the meanwhile I am wondering whether changing the lens will reap any additional rewards.
for the purpose of this comparison, I'd like to ignore cost and weight.

I've included the 200-500 in the comparison, because by all accounts this looks like an absolute beast, but beyond a single review from "Juan", I cannot find any real tests or recent reviews of this one, so interested if anyone has any experience of this too.

Thanks in advance!

 

[gramps]

I too was a bit disappointed with the Sigma 300-800, yes it gave brilliant reach but the image quality just wasn't 'up there'.
I recently sold it and bought a Nikon 500 f4 VR and the difference in image quality is amazing ... I am sure that the Canon 600 f4 would demonstrate a similar improvement in image quality, though of course I have no experience of using Canon

 

[Icee]

I have users the sigma and felt the same as gramps about the iq.