StuffIt? Bah. Unless you need to unarchive .sitx files, StuffIt is useless, IMO. If you're doing something more than .zip files, I'd recommend The Unarchiver. If you're just doing zip files, stick with the built-in support; it works just fine.
I hate StuffIt and the company that makes it. You can't download Expander from their website without providing an email address to which they automatically sign you up for their junk mail. Thanks but no thanks your product isn't that good.