First big reason is stability. You can't beat the size of Libec's HFMP Video Monopod Feet. Second reason why I would choose the HFMP over the XPRO is because you can quickly Lock / Unlock the base with a simple stepping motion.
Now if you were to purchase the Libec HFMP Combo which includes the TH-X Dual Mount Video Head, you're getting a fully operating head with Pan and Tilt controls, whereas Manfrotto's kit will not have a fully functional head. With the TH-X Head you can then use it on a Slider (as seen here), on a set of Tripod Sticks with a flat 3/8" base, or even on a Tripod with 65mm half bowl.
The feet on the HFMP Monopod is removable along with the Fluid Head, so you can separate it if you have to break it down. The Libec HFMP Monopod KIT not only includes a video head and carrying case, it also includes a bowl clamp for 65mm tripod usage and a hexagon wrench for preferred adjustments.
It's possible to purchase each of the Libec HFMP or Manfrotto XPRO Video Monopods without a head and you can add your own. The benefit to Manfrotto's is that it collapses 5" shorter, extends about 5" taller, and is about 1.2lbs lighter. But if you're looking for optimum stability nothing currently compares to the HFMP. Libec is also bringing better value at cheaper retail pricing than the XPRO system.
This Special Tripod Leveling Adapter Can save you hours and speed up your workflow.