Want to jump in real quick with a small anecdote - I'm somewhat new to the guild, not to RPing.

The way I see it here is, at this point, the difference is purely who you want to net in your IntCheck and actual RP. I'm currently running an RP that's posted some pretty damn long posts (which might change soon) in a short amount of time. I don't think I ever would have caught the same audience if I had posted in Advanced, which seems to fit the amount of lore that my co-GM and I built for the world. I think I would have at least gotten people that tend to post at a slower rate if I had made my RP Advanced instead of Casual - not that there's anything wrong with that, of course.

That's the main difference that I see - obviously there are different post lengths, qualities, guidelines, but at this point I'd wager that people cast their net because of who they want to catch, not because of lore reqs.