We've done the SVI twice from CYOA in St. Thomas.
Much smaller crowds than the BVI, fewer beach bars, more secluded beaches.
There are a number of power-boaters that all magically disappear about 4pm, leaving the anchorage to you.

The sailing is more "open ocean" style than the BVI. I found navigation to be fine, but things are maybe not quite so well marked. If you can find a Cruising Guide from about 2002-3 time-frame there's an SVI section.

In general you'll feel a little more "on your own" in the SVI, which I feel is one of the allures.

Probably should add: Tough to do this in 7 days from CYOA, but you certainly can. Ten days preferred, and a stop at Marina Puerto Del Rey around mid-trip to fill up on fuel and water / Heineken as required!