The one that uses the U bolts is the older style Dual Cam that is not being made anymore. Nothing wrong with it at all but some people had a problem with mounting it because the large U bolts interfered with the propane tank mounts.
Both styles perform exactly the same. The are mounting and adjustment differences only. I had the old style for quite a few years and was very satisfied with it. Never had bit of problem either adjusting or installing it. In fact, I prefer the old style to the new one because I feel it is a bit more rigid and stronger where it mounts and the cam arms are more robust.
Those older style Dual Cam units are becoming quite hard to find now.
Barney
New Style (has been updated from this picture)
Old style
Old style on my trailer