I own both. The quick and dirty:
Ergos: PM2 by FAR. The GB has next to nothing stopping your hand from sliding onto the blade, which is odd, considering its "intended use".
Blades: The GB can't be beaten in this category. By anything. The geometry is spot on, the M4 stays sharp FOREVER, and with a small amount of effort, may be the best slicer you'll ever know.
Locks: The PM2 has it. It's near Axis-Lock easy. The lock on the GB is strong, but absurdly difficult to access. I had to Dremel a cutout into the liner and slab in order to make the knife EDC worthy.
Fit and finish: GB by leaps and bounds. I needed to disassemble my PM2 to remove a metal burr from the liner that was marring the bronze bushing. The edge grind was also funky, and the pivot tension took forever to set properly due to the number of screws in charge of the tension.
Weight: PM2.
Use: Contrary to what most people think, I'd trust the PM2 for heavy tasks over the GB. Thicker blade, thicker behind the edge, and better ergos for imparting force. Also, when you compare them, the PM2 has a more robust tip. Unfortunately, force destroys the S30V, so that's a moot point. If Gayle had given his knife a deeper choil, some light jimping, and a blade as thick or thicker than a PM2, I'd trust myself with it a little more.