Big Zoom Question Sigma/Tamron

Sigma 50-500, 150-500, Tamron 150-600. Which one is sharpest at its longest focal length?

Kinda hard to really compare a 500mm to a 600mm.......

I have, however, compared the Siggy 50-500 and the Tamron 150-600 with both at 500 and found the Tamron is just a hair sharper.

I have the Sigma 50-500 non OS (older model). I struggle to get sharp images at 500 but on a tripod, high shutter speed and use MUP to expose it is possible to get a decent image. The newer models with Stabilization (probably better optics also) seem to be performing very well in the reviews in comparison. I am going out to shoot some birds and wildlife this coming Friday so I'll see if my technique has improved.

Welcome to the forum,difficult to answer as all 3 are good lenses,i decided on the Tamron due to more reach and later design.

Sharpest? The Sigma 150-600mm Sport, which you didn't list.