I have a Maxx, and am a huge admirer of the Manix. With a 5.5" blade, for defensive use, it's hard to beat the Maxx. Carries deceptively easily due to the thinness, but the handle is still 6.5" long.
I find the Maxx a pain to use for utility use. Pulling out 6.5" of handle, swinging that giant machete open, making a quick cut -- especially if it's got to be precise, keep in mind the blade tip is like a full 6" from your hand! -- and then closeing and returning to pocket. That is a freaking chore. Normally when I carry the Maxx, I always also carry a smaller blade for doing most of my actual cutting (something easily carried like a Chive or Spydercard).
So, in summary:
Pure defense: Maxx if it's legal in your area, otherwise Manix
Defense/utility: Manix by itself, or (if it's legal in your area) Maxx supplemented with a smaller knife
Joe