The 6" allows a shorter (lighter) piston. Whether that saves any total weight (i.e., substituting .30" of steel beam for .30" of aluminum skirt), or reciprocating weight is a different question.
It should reduce shaking force very slightly. You can away with a tiny bit shorter skirt since the side-thrust vector is reduced.
These are all very small changes but all positive.
The negative is that it also increases knock sensitivity, and reduces DCR for the same IVC and static CR.
What I'm still trying to make sense of is the effect on breathing. Popular opinion is that with a small/restricted port it helps by extending the period of vacuum over more degrees of rotation (and won't help if the port is generous, like BBC). What makes it complicated is the fact that for the Gen-3 both the port and bowl are not bad, but "busy" (siamese).
