I have the Sigma 450-600 Contemporary and think it is terrific. Pictures are very sharp but I do use a tripod. You might want to consider this one too. The best way to decide is to get all the lenses and test them side-by-side. I know it can be a lot of work and expense but that way, you know what is the best buy for yourself and not going by others' opinions and needs. Good luck.
I think you had a typo. I'm sure you meant the 150-600 Sigma Contemporary, and yes you are spot on, it is a superb lens.