...Not much, really, except that there'd be some input by the writers beforehand so it might be more likely to have stuff on it you'd like. Also it might be slightly more encouraging of weird pairings, which, er, I like, in general. Trying to list all pairings I might possibly write is always my problem with reversathon ads, and "any combination of x,y,z..." often doesn't catch people's eye.
Although that really depends on the people prompting, I suppose. There's no induced randomization like in 0tp.
Also just pairing + kink isn't much of a prompt for a full-length thing.