I bought the WoodMaxx FM-54 on sale, and with the $1,000 saved (vs a 52" Del Morino) bought two extra sets of hammers, top-and-tilt kit, and Pat's Quick Connect.
If you didn't read this elsewhere already, since you're cutting brush and saplings you'll want hammers instead of Y-blades.
I'll note the FM-54 manually side shifts "a little," though I probably won't need it, and if I do would likely rig up a hydraulic cylinder. The specs are somewhat misleading, if memory serves the FM-54 shifts left 3" off-center and right 6"; that's not a lot, but WoodMaxx flail mowers seem to sit close to the tractor so the PTO shaft likely would lose a lot of power if it shifted more. Assuming I'm correct the benifit of sitting closer is less felt weight on the 3-point.
I cannot speak to any build quality differences as they're still building my FM-54, that might even out the initial difference in price.
I do not know if this is a valid concern, but from experience most quality imported parts to the U.S. are comparitively spendy and WoodMaxx replacement parts seemed "reasonably priced."
Respectfully, I wish I could provide more than "food for thought," hopefully other members will address the above as I'd also like to know.