Really, it kinda depends on what you are towing. I towed a 8000lb boat out of China Lake in Maine with a 4 cylinder S-10. I did it with a manual. The auto of the SAME truck couldn't get it out of the water.
That's my take on towing with a stick. I towed giant artillery pieces with a manual 5-ton in the corps. I towed the same thing with the automatic 5-tons and the manuals seemed to handle the task a bit better. Granted - it's probably all in my head - I want a manual, even for towing.