That's weird. Just comparing the power boards, there's no obvious reason as to why the MMM would have less punch than the MM (it has less on-resistance than the MM so should be even punchier, as others have reported). Maybe Castle refined or altered the back-EMF detection hardware so that the Monster would be smoother than the MM even with the same firmware...and maybe that's what you're perceiving as "less punch"?
If it's not your setup, then perhaps it's just a preference of yours...but many others have reported the Monster as being punchier than the Max when used in the same setup.