In my experience, it's really going to depend on the gorg. Photosynthetic gorgs are relatively easy to keep, as long as algae doesn't build up on them. Non-p are a lot harder, and require regular feeding.
As a very general rule, if the polyp color is tan, it's probably photosynthetic. If the polyps are white or colored (like Dendronepthea sp. corals, for example) they are more likely to be non-p. I'd be wary of the LFS's classification - they are often wrong. I bought a "photosynthetic" gorg with
white polyps. IT started to go south at about 3 months, I started feeding it regularly, and now the polyps are tan (like they probably were before the LFS got it.) Weird.
Good luck - they're beautiful, but the unfortunate prettiness rule applies: the more beautiful the piece, the harder it is to keep.
Just my 2c,
Danielle