Right, so, I can't sleep, so I thought I'd add a few notes.
Cateye Opticube: LED front headlight. Takes 3AAA. Steady and flashing mode. Bar mounted. Cateye says completely waterproof (can be used as a diving light to 30 ft or so, they say.) ~$30.
Princeton Solo: Halogen *headlamp*. Takes 2AA. 2W light. Steady mode only. Head mounted (with elastic straps.) Water resistant (can take a dunking, I think, but don't use as a diving light.) Has two reflectors: spot, and diffuse. Two bulbs come with it, higher and lower brightness. Tested in the higher powered, diffuse configuration. Can be had for p < $30.
Princeton Vortec: Halogen *headlamp*. Takes 4AA. 4W light. Steady mode only. Head mounted (with elastic straps.) Water resistant (can take a dunking, I think, but don't use as a diving light.) Has two reflectors: spot, and diffuse. Two bulbs come with it, higher and lower brightness. Tested in the high powered, spot configuration. Can be had for p < $40.
At first blush, these lights may not seem like they make for an apt comparison. The last two are sold as *camping* headlamps, after all, and the Cateye is a bar-mounted front bike light.
However, the comparison is more sensible than it may seem. Each of these represents a different sort of route to battery-powered, low cost lighting: on bike, on head, and brighter on head.
Moreover, these are the lights I had on hand, so that's what's getting compared. If you don't find it useful, ask the moderator for the money you paid for the review back. Anyway, the Princeton lights give some idea of how cheap halogen lamps compare to the newer LED's.
I use the Princeton Solo for camping. The Princeton Vortec is my backup bike light should my HID bar lamp crap out. I take it with me on all of my night rides. It's nice to have, furthermore, if I get a flat and I need some light to make repairs. The head mount is especially useful for that purpose, as it leaves one's hands free.
Each of the Princeton lights is a reasonable backup option for me, because I usually don't wear a helmet (gasps, howls of outrage, and whining are better directed to a helmet thread.)
So, first, the most important matter: lighting.
The competition involved turning the lights on in a fully dark room, at a white wall maybe fifteen feet away (that's ~4.5 meters for the Canucks). The first two lights have brand new batteries, the Vortech has a set a couple of hours old.
Surpisingly, the dimmest of the three lights is the Cateye Opticube. With much-hyped improvements in LED technology, you might guess it would do better than at least the Solo. But no. It loses out in a close competition to the Solo, a 2W halogen light.
I could see more detail on items a few feet away from the point of illumination with the Solo than with the Cateye. The Cateye's bluish light seems ghostly, and pale, compared to the more jarring yellow of the Solo's halogen, but the real difference is the slight difference in illumination.
The Vortec blows both of them away, and provides startlingly good illumination out to several feet further away from the wall than the other two. Indeed, from my riding experience, the Vortec in the high powered, spot configuration is an adequate backup headlamp for *seeing* the road. It's a brighter light than generator headlamps, for example. It's not reasonable to ride at daylight speeds with it, but it's bright enough to use to get yourself home at somewhere v<14mph or so.
Secondly, ease of use:
The Cateye wins here, since it attaches very easily, with a rubber friction-locking strap, to the handlebar. It switches on and off with an easily reached switch on the surface of the light housing.
The Princeton lights are not difficult to use, really, but you do have to put them on your head, and the Vortec's weight is not negligible. Some people might not find it comfortable for longer rides.
As a bike light, the Cateye also has the advantage of a blink mode, making for better visibility to oncoming traffic. The extra height of the Princeton lamps, and their look-and-point possibilities, do make for some attention-getting, too, though, it should be said.
The headlamp is obviously preferable for doing roadside repairs in darkness.
It's surprising that the LED light is outclassed even by a 2W halogen light. But it is. And the Princeton lights aren't cheap for this sort of light, either. WalMart's got 2W headlamps for under $10. So, if you're wondering what to do for a very low price lighting solution, don't overlook a headlamp.
The Cateye's flashing mode is a nice thing to have for riding in traffic, and makes a nice adjunct to a brighter headlamp.
Overall, I like the Princeton Vortec as a headlamp among the three. It's brighter, it can be used to illuminate dark roads, and it's more useful for things other than riding a bike.
Some links to the products: