I have used both speakers. Both are nice, depending on what you want. H-75's have more sizzle and a tighter bottom-end. M-65's are woodier and warmer. I prefer H-75's because they're loud and proud. M-65's have more of the traditional Greenback vibe, and they're noticeably less efficient, so they let you crank your amp more, if that's what you want.
Both were nice with my EVH and my Krank.