Another quick test while waiting for some birds. Shooting neighbors brick wall with the D2x and the 2 lenses mounted on Berlebach UNI-16 with Wimberley WH200.
The Sigma shows slightly better details than the Tamron. Subject distance was around 10 meters.
First the Tamron 150-600 after normal workflow in Lightroom.
Now the Sigma 150-600 also with normal workflow from Lightroom.
Next 2 pictures showing same as above but with any post processing applied.
Here’s a side-by-side comparison using Lightroom screenshots. The Tamron is better on the right side, everything else, the Tamron does not have a chance when compared to the Sigma. The Sigma is on the left side while the Tamron shots are on the right side.