Time constraints aside, I probably wouldn't sign up for a gen bigbang for the simple reason that I can't predict whether or not a character will end up in bed with another when I start writing a story. (*squints* run-on sentence. Sorry.)

Unless the whole point is that they get together.

I do realise that this isn't how it works for everyone.

Anyway, I think pairing or trope-specific bigbangs (kinkbigbang, au bigbang, apocalypse bigbang) are a good idea, but I wouldn't set them up as a rival. What? Why? What for? I saw the post you're referring to and it made me go O_o for this reason. (Well, more for the other reasons, which we're not mentioning here, actually, but *waves hand* not going into it here.)