cfischer sorry to chime in with a comment lacking personal experience but, looking at the reviews of these lounges on Yelp/LoungeBuddy, it looks like the VS Clubhouse will be worth the trouble if the CL is at-capacity. The UA Club at T3 seems about as barebones as lounges get.

Hopefully bumping this post will attract someone with experience doing so, but getting between terminals at SFO seems very easy (apparently International A being the only one where you'll need to reclear security). With Clear/Precheck available to you, I think that largely mitigates any concerns regarding timing or inconvenience.