I decided to buy all three because every one online was telling me different storys. Lets not forget Tony Northup videos on youtube would contradict himself on later videos. I tested them out in the field and in my home in my home studio. I concluded while I liked the tamron the most due to its design and I liked its tripod mount a lot I found at 600mm is was far to soft for my needs.
After testing the sigma C I noticed both the S and C was very similar in quality in fact when it comes to the photograph I could not tell them apart between 150mm-500mm in fact it seemed the C was a bit better. However once I started looking at the 600mm end I noticed the sport was only slightly sharper and only slight so slight alot of people would not be able to tell the difference.
In the end I decided to go with the Sigma C because it was very close to the sport in image quality and over 1KG in weight lighter. I thought I could carry two cameras instead of one very big lens.
I have also come to a conclusion which is casing me alot of un-sureness. As you guys know I did own the canon 100-400II grey import. I was convinced some thing was wrong with it but when I tested another copy in store focus was still slow. camera used 7D and 600D. After much research I have come to the conclusion that it is possible their was nothing wrong with the lens. I have learned that some cameras may not be delivering enough power to the auto focus motor. This also would account for the battery's not lasting very long when I used the lens. This also means the critics who defended the lens may be right to do so.
I did see a video of a 1DX using the lens and the auto focus was like 3 times faster than my combo. I really think canon should have addressed this issue. So I hope my findings help some people out their. It seems budget cameras or older cameras body's may not be up to the task of using this lens at its full potential.
It is worth noting that when testing the auto focus speeds on the 7D on all three 150-600mm lenses I did not notice any speed slow down compaired to other videos I had watched.
Some people have said that the 150-600mm lenses are not sharp lenses. I dont agree it depends how you use the lens getting closer to your subject can make the worse lens the best.
