That's a tough one, Sideshow has it's benefits, but often, Toys 2 get figures at least a month before Sideshow. If you want it quickly, Toys 2, if you want benefits, Sideshow.
IMO, the benefit is getting it before everyone else. That way...if something is wrong with the figure, it won't be hard to get a replacement.
Oh, and does the Predalien have mandibles on its inner-jaws too? I can't really make it out.
Based off of the Predalien-buster in AVP..... it's supposed to have them.