It depends on what you’re trying to do.
PZ2 files are optimized to work specifically with M4 or V4.
BVH files are designed as a “general-purpose” motion capture file to allow people with other figures or software packages to use our mocap data. They will work, but are not optimized for the characters so you may end up having to do some tweaking.
Our latest release, Swordplay, has PZ2 files for Genesis, M4, and V4, as well as Aniblocks for all those characters. We will be using this approach for all future packs. Also, we plan on updating the older packs with Aniblock and Genesis data in the future.