After wearing the PASGT for several years, I went with the MICH/ACH for the higher profile cut, lighter weight, and improved suspension. Of course you can pick up a PASGT with an upgraded suspension or a skate helmet for much cheaper depending on your application (as several previous posters have stated).
Any way you go a newer type padded suspension system is the way to go. The old suspension systems in the k pot (and older) got really uncomfortable after several hours of wear (but left a cool parachute cord donut on your head).
The MICH does well for keeping my head free from any real dings from low vehicle doorways, crossbeams in crawlspaces, and the errant falling random whatsit including, but not limited to, carelessly swinging rifle barrels, things falling out of the pouches and pockets of the guy (or girl) above you on a rope of ladder, propping up MRE heaters, and as a real convenient place to mount a white light when I need to see a patient, not to mention the palistic protection it affords.
Application should be your final determining factor though. No point in ballistic protection if the only thing you're getting shot at with is a camera.