I run only the Black Diamond Gemini for adventure races over 24 Hours, and use both the Gemini and Petzels for SAR. I really like both, but if you want one as an all around, I'd highly recommend either the Duo (if weight is not an issue) or the Gemini (if you want to save a few ounces).
I would stay away (READ: Avoid like the plague....) the Princeton Tech headlamps. They make great flashlights, but the headlamps are, IMO and experience, woefully inadequate in burn time and battery life, as well as bulb quality. (Ask me how I got to do a 250' free rappel in the dark...

)
That being said, I have found the leds to be merely adequate for fast hiking at night. Additionally, be very aware that you do not get good penetrating light with leds. They're really good for map reading or close work, but if you're moving fast over rough terrain, or on a trail where there is risk of ankle injury from rocks, etc. you'll want a regular bulb. Halogen is fine, but only for occasional use, as the burn time for most lights is only 3-5 hours with the halogen bulb. Obviously this is not long enough to get you through the night without spare batteries.
The new Petzels, with 5 leds, seem to be a good compromise; however, I haven't had the opportunity to use one in the field.
This is where the Gemini really shines. The led is pretty weak, but adequate, the normal bulb has a fantastic burn time, and there is a backup halogen bulb in the battery case.
Another hint. Drop the coin for lithium batteries. They last longer and are lighter then regular batteries.
HTH
-H-