Can't comment on thr Maui Sails boom, but I have X3, X6 and X9 models of the NP boom. The X6 is an excellent compromise on performance vs. price. It is made in a higher-spec aluminium than the X3 booms and, with its carbon end piece, it's almost as stiff as a carbon boom (but at much less price).
I use mine on a 5.4 sized sail, which, in my location, is a cross over size for slalom and wave conditions. In slalom, the extra stiffness can be felt most noticeably during drag races. In waves, I'd have to say that the stiffness is not that noticable.
An excellent feature, is the fully-articulating head, which allows the grip of the head to always align perfectly with the mast.This reduces point loading of the mast, increasing its life in this area.
The back end adjustment is easy to accomplish, even with cold fingers.
In summary, my X6 is excellent for use with slalom sails down to 5.4m, where its extra stiffness is almost as good as a carbon boom.
Perhaps others can comment on its use in wave conditions better than where I sail?
Hope this hepls,