Not much to say. The Lenstip review shows that there is not much to choose between the sigma and the Tamron. Tamron has better resolution at 600mm and f8. I'll stick with my tamron.
At this point I may just get the Sigma 150-600 Sport, the tests on that one look pretty good.
It will be nice to see tests from more than one website though.
I expected the Sigma 150-600 Sport to be as sharp as the 100-400 II, which is not a lot to ask with the ART series outperforming all except the Otus, but after i saw the images at TDP I lost all interest in 3rd party telephotos, so since the Sigma 150-600 C is the lower end, its doomed to perform even worse.