What are the pro's and con's to each . And what gains are to be had from using a windowed piston in 372/385/390 or for that matter any saw that comes with a nonwindowed piston
Non-windowed -- allows wider ports. But requires open transfers or transfers that extend into the case.
Windowed -- gas flow through piston helps cool piston. Transfer ports perhaps less complicated to cast into jug than the kind that extend into the case ?
I'm not sure that there is any clear advantage in power, since both designs seem to be capable of similar power, except for the port width limitation.