It would make sense for the 5v5 ladders to be infantry only and on domination as there aren't any helis/jets & vehicles. Though Rush w/o tanks, LAVs, jets and helis and only 4x4s sounds like it could be fun.
Slin, to answer your question, yes and no. Yes there's a difference when you consider the fact that at the core, both games themselves are extremely different. So naturally that will play a part in how they're different. And I only say no because they might be playing rush in the competitive scene, which is almost 100% identical to CoD's Search and Destroy, with the only major difference being that you have to destroy a set of two bombsites 3 different times, whereas with SnD you only have to successfully explode the bombsite/successfully defuse the bomb w/ a round limit of like 12 or 14 (don't remember, but there are a shit ton of rounds).