Cocoatech’s Path Finder is a major upgrade to OS X Finder, at least if you’re the kind of user who finds things like Path Finder userul. Path Finder 6 is a major upgrade to Path Finder.
(Incidentally, the .sitx archives created by Path Finder—and, of course, Stuffit—are actually smaller than the comparable .zip, .tgz or even .tbz files. And not by a small amount. PF6 appears to have upgraded to the newest Stuffit engine, though, which means it’s making .sitx file that only it or the newest Stuffit can open.)