I've been commuting in the pitch black for 6 years now. It gets dark in Alaska. I've been using the Performance dual for most of that time. Since I'm riding on studded tires, my speeds are normally under 20 mph except for some downhills. Speed doesn't seem to be an issue at lower speeds.

That said, I've recently switched to a NR Flight HID w/ the Lithium Ion battery. The battery is really small and I use the highest light level on my 20 mile (one way) commute. The light level remains the same even though the battery is weakening. I have no idea how long the battery lasts between charges yet. The ride is just under 2 hrs one way. The HID light is so much brighter with better coloration that I feel much safer riding between the moose on the trails now.

Also, I have 3 mounts for the light. Handlebars, helmet, and then a headmount strap for skiing on unlit trails. I haven't tried that yet but it's been snowing for a few days now and I'll let you know how it works.

I have several LED headlamps also (as I said it's dark in Alaska) that are reliable but definetly much less light output.

Although HID's are still relatively expensive, my vote is HID. (so far the NR seems to be a good product). I got mine on ebay for around 60% of retail including shipping.