The Versa-Jack is just a fifth jack on the back of the sound card. You can use it for a few different things (i.e. center channel speaker, headphones, etc...) I plug my headphones in it. When I want to use my headphones instead of my speakers, I bring up the Santa Cruz control panel, and just change my sound output from "4 speaker" to "Headphones (VersaJack)".
Yeah, I know about the extension cord setup. I've used it before, but I'd rather have my cluttless desktop. Besides, the versajack is easier.
I guess what it comes down to is what I'd be gaining by switching cards. The Santa Cruz is an excellent card. Yet... I am very curious to compare the two.