Michael
I think both clubs/courses could work well as a venue however I tend to think you are looking at RC through Savardi-tinted glasses.
RC has the not inconsiderable constraint of walls and trees in providing access points onto the site. RC has abrupt elevational changes along the new 10th hole which may make things tricky for moving spectators around although CS managed it with their water side holes. Just pointing out Gullane doesn't have the same issue.
More generally RC requires a bit more of a trek with the 10-13 being out on a limb as are 1-4, compared to the the relatively compact routing of Gullane. Gullane is much more open and I can imagine a stand on top of Gullane hill providing a panaramic view over the whole course. Easily enough space between holes for crowds.
As for off-course facilties, Gullane might not have the same amount of floor space but they have just spent £1.8m on their clubhouse (possibly no coincidence) upgrading it, adding more accommodation etc while they have the "visitors" clubhouse over the road. They also have far more space generally for all the technical compounds and I would imagine they wouldn't need any additional land from any other landowner. In that regard I suspect RC may, not that it would necessarily be a problem but may be something they would have to contend with.
Someone else suggested why play on a composite course meaning Gullane but is that not what RC is now to an extent ? I don't think anyone would suggest that the composite course at Royal Melbourne is a compromise.
Niall