I think a lot of predator people will have to jump ship if they sign up for an LE Metallica, but I doubt skit-B will hurt because of it. They have said they have nearly 250 people on the waiting list, and there are only 400 Metallica LE slots. So almost all of those would have to be predator buyers who jumped ship, and that's unlikely.
Now there can be unlimited pro's and premiums, but it would be illy to jump off predator for one of those, because they will be available for a long time. With Metallica demand, look for multiple runs like they did with acdc and Tron.
Right now, Metallica looks like the cooler game with more going on. Maybe Predator gets some layered "Special Force" type jungle plastics or something and the whole package looks better in the end, and there is much to be said about never having another opportunity to get one, but I have a feeling Metallica might join the ranks of truly great modern stern like acdc and Tron. Just my .02.