Yes, the 1957 bearings were better and by the time OMC was producing the 28,33 and 40HP motors in the mid 60's they had them figured out.
The 1956 bearing is a full complement needle bearing. There are many small needles that make up the full diameter of the bearing. The only thing that holds them in place is the outer race of the bering that is drawn over and crimped around the ends. A full complement bearing is great for high load applications (because there is more bearing surface) but has shortcomings in a high speed application. The needles are more likely to try and run out of square to the inner and outer surfaces.
For 1957 and up they went to a caged needle bearings. This has gaps between the needles and they are held in place by a cage that can spin withing the end of the rod. This bearing is better suited to high speed. The later bearings are also wider (the small end of the rod is wider) so the later rods wont fit the earlier engines unless you machine the back side of the pistons to expose more of the wrist pin.