Part 3 of 3
Finally, here are my 100% crops of the RRS BH-55 (left) and Acratech V2 (right). Camera settings for all were f/8 at 1/15 sec using the Singh-Ray Vari-ND to balance the exposure.
If you look carefully, the RRS crop looks a little sharper IMO, but the difference is pretty hard to see. I suspect that any differences would be more apparent with longer teles, longer exposures or perhaps higher resolution sensors.
Under these fairly benign test conditions, there seems very little difference between the two. However there is more to these ballheads than just stability.
Operationally I found the RRS ballhead to be much easier than the Acratech to set precisely. For example, I centered the lens on the same spot for all captures. Using the Acratech, the lens would droop very slightly after I tightened the controls and I would have to compensate for that. With the RRS there was no droop; tighten the controls and the lens didn't move at all.
At this point I am going to keep the Acratech V2 and use it for my hiking and backup ballhead. But the RRS will be my primary ballhead for those times when maximum stability counts and weight is not a factor.
Hope this helps,