2 lights - one head and one bar. Brightest light on bars for depth perception, less bright light on head for seeing round corners.
Currently using an Exposure Strada (yes I know it's a road light but it just works!) and Diablo headlamp; rarely use the Diablo on more than medium though as it just seems to "blow out" detail on full.
2 also gives a bit of a safety margin and you can manage them to give longer burn time. That said, not had probs with Exposures but I have had a few older lights that run flat unexpectedly or have been damaged by (ahem!) impacts or water getting in there.
And trust me, you don't want to be at the bottom of Deliverance with some broken lumicycles and a micro headtorch.