The Mad Dog MD-8XDVD9 v2.F9 is the original Mad Dog firmware. The second one, ND25x0 2.F9 RPC+RL, is a modified version in which the name was changed to NEC 25x0, to make your drive show up as a ND25x0 in you bios. And it has the riplock removed and is region free. I would choose the second one.
Both firmwares are single-layer and dual-layer bitsetting.