Is owning the club worth it if you seduce and side with Garth? Or is there just that much more content on Galiano's route? I didn't expect him to go up to $100k and offer ownership.
Never tried to own it, but I don't think it changes much story-wise (I think you can give the place a different name if you own it?). Alternatively, saying you're helping him for ethical reasons gets you more approval from him. You can also visit Galiano in prison. Also I might be mistaken since it's been awhile, but if you go with Garth, if you don't recruit Phoenix (not that I like his character much) before raiding the club then he dies I think?
I'm not sure just how much more content there is with Galiano's route, but again, it's mostly (if not entirely) just Galiano-specific content rather than anything more generally story-related so doing either won't do anything like impede overall progress.