[jbuchert]

What I have heard over the years..

Less side loading on the piston/cylinder wall. It also slows the process of the piston changing direction holding the piston at TDC for a few degrees more crankshaft rotation allowing more A/F mixture to enter the chamber. And weight of the piston as mentioned.

Some argue to put the longest rod you can fit into an engine. I think there is a point that it becomes pointless and the gains arent measurable.