I use the PT Apex, with some velco straps around the side holes to keep the elastic headband from sliding off the hard hat. The light is on the front of the hat, just above the brim. It can be angled down to shine where you are looking. Be sure to get a headlamp that has adjustable angles.
Most times, the standard LED's are more than adequate. If you need throw, the center LED is great. And the Apex (or EOS) can be upgraded.
The only problem is weight. The Apex gets heavy after several hours of use. The Apex Pro would be lighter, since it's got (2) CR123's, instead of (4) AA's. Either option gives you more brighter light options, and better runtimes than AAA lights.
For my work, I rarely need throw. I also carry a Fenix P3D as my primary light. I'm likely going to get a Zebralight H30 for the hardhat. The weight is insignificant, and can run for days on low. I'll probably use the Zebralight for backpacking too.