I have used both with great sound. The rhodium is somewhat more neutral to my ears. If you are going the GTX route, I would strongly suggest you also purchase the GTX aluminium backplate with 104 D stainless steel/carbon cover plate. This is what I am currently using to feed all of my gear and these have greatly reduce RF/EMI noise whcih has translated in black pitch audio background letting new low level musical details pop up. This was one of the best and most satisfying tweak used in my system. There are a few threads on the Gon on this subject.
Gold or Rhodium
Have you compared the Furtech wall outlets? I am setting up a new dedicated room and need five wall receptacles; one for front-end sources, one for each monoblock, and two for subs. Each outlet will be on it's own dedicated line. Will use the GTX-D series. Question is should I go with the gold or rhodium plated or use a mix of the two? I've read that the gold offer a slightly 'warmer' sound but gold is soft and can be easily melted off if any sparking ocurrs.