I've read quite a few--but not all--of the entries on this thread. I've seen similar discussions on many other forums. I offer my experience and opinions with no expectation that anyone will agree. I'll describe my setup, too, as I can't see anyone on this forum using exactly what I have.
Context: I'm late '50s; I ride 200-450 training kms a week in all weather and at all times of day on bike trails, city streets, highways, and country roads--incl'g gravel; I sometimes take my bike "off-road", but I'm certainly not a mountain biker. I also ride Audax. So I'm sort of a long-distance commuter; I wrote 'training' above 'cos altho' I'm by no means fast, neither am I simply meandering along: I generally want to get somewhere in a given time and at a pre-determined pace.
1. Personally, I find most of the lights used for city 'commuter' use inadequate (dim; short battery life; poor weather protection; bad mounts &c) and/or over bright and/or distracting rather than, well, illuminating. As a driver, and esp. as someone who regularly rides and walks on commuting trails at all times of day and night, I experience bright front lights as excessively bright, indeed blinding. I find it hard not to feel these lights as 'aggressive', tho' of course most people using them are by no means aggressive. I have a similar reaction to blinking/flashing lights--esp. those that have an ultra fast flash cycle. And I find it more difficult--not impossible, *more* difficult--to judge the distance and speed of a bike with a blinking/flashing light than those with a steady light. While I concede that flashing lights can attract attention in traffic I find it's easy for me to lose track of them.
2. While initially satisfying, I find using an ultra bright headlight when riding on roads or tracks away from street lamps or overhead lighting eliminates my vision of all that's *not* in the beam. That is, while I like being able to see things in the bright beam, I feel like I'm in a tunnel and have a good chance of missing whatever's off to the side. If what's off to the side is a fast moving animal this can be dangerous. This means that to ride safely with a very bright light at any speed, the beam needs to be very very wide as well as long. Whenever I encounter people using these kinds of lights on commuting trails or roads, I am inevitably blinded by them. Whenever I've used such a light on the road or trail, people complain: sometimes verbally, sometimes through flinching and cowering, sometimes by repeatedly flashing their lights at me. And my eyes don't adjust well to the dim areas.
3. With the above in mind, and after using many different types of lights, I've settled like some others on this forum on a combination of battery lights and a hub dynamo with European spec. head- and tail lights. After much research, I got a Philips Saferide 60 headlight, a Spaninga Lineo tail light, and an SP-PD hub dynamo. I also have a Shimano DNH-380 hub dynamo. For back up, I carry two Portland Designs Radbot 1000w rear tail-lights, and a Planet Bike Blaze 1w headlight.
At the front, the Saferide is on the fork crown; the Blaze on the right side skewer and angled towards the ground.
At the rear, I have set up the Lineo so that it can go either (a) directly under my saddle; or (b) on any of various saddle bags I use. I have mounts for the Portland Design lights on the seat stays near the brakes, and on the mudguard eyelets near the axle. I usually keep one light on the stays, one on the axle.
Ninety-nine percent of the time, I use the dynamo lights on their own. The front light is excellent on trails, city streets & highways, and country roads. It provides a relatively even and brightish beam far enough ahead and to the side to not have me feeling like I'm in a tunnel and to allow me to descend with safety at speeds more or less like I would in the day. The beam has a 'cut-off' so that if it is correctly adjusted it wont dazzle oncomers. There is very little hot spot. I have only ever once been abused by someone for having too bright a light and that was after I'd accidentally angled the light upwards. It took me only a moment to fix it since I can easily adjust the light's throw and spread by swivelling it on its mounting. On country roads, oncoming cars usually dip their beams for me; no one has ever repeatedly flashed their lights at me. The rear light is visible from a long long way and provides a steady beam, but is not so bright as to be blinding.
Despite what many others write, I believe I *can* feel the resistance of the dynamo hubs through my legs; however, I don't believe they make any significant difference to average speeds &c. And at night, far from home, I completely forget about any imagined resistance and revel in having strong, secure lights that will not run out or stop--unless I somehow break the wires or connections (I never have, touch wood). In the daytime I turn the lights on if I'm on a busy road, on a hazy day, going through tunnels, riding along a busy bike trail, or making a long descent at speed. It's simple to turn them on, simple to turn them off. They have never failed me.
The battery lights are mainly there as back-ups. I rarely use them (< 2% of the time), and only in combination with the dynamo lights. To be honest, I think the Radbots are *too* bright for most use, especially at night, esp. commuting at low speeds in the inner city. I say this after riding and driving behind them when they were on my partner's bike. I keep them 'cos it seems wasteful to throw them away, it's good to have a backup when far from home (mandatory for Audax), and they are excellent to use as torches when doing repairs or fossicking about at night. And I sometimes use one of them in the *daytime* on busy roads in heavy traffic. When I use them, I use them on steady. I've set up the front light so it points just ahead of the wheel; it's there as a back up. Except to test it, I haven't turned it on for c.18 months.
4. The fellow from whom I got the dynamo lights and the SP hub conducts many long range tests and reviews of dynamo lights and hubs.They make interesting, if sometimes too detailed, reading: http://swhs.home.xs4all.nl/fiets/tests/ ... ex_en.html
. There're also many, sometimes interesting, discussions on the candlepower forums.
5. It's important to remember that many bike shops and online retailers have vested interests in the lights they sell and test; and they are often not well equipped, either conceptually or in lab. resources, to conduct a test. I've had many a bike shop mech tell me "Brand-ABC lights are great, they're the brightest there are! You need the brightest lights you can get" And so on. I stopped believing anything bike mechs told me in 1978. It's saved me a lot of money. I like the SWHS tester because he provides a lot of detail, tests long term, is reasonably up front about his assumptions and the limitations of his and other testing processes, and references the European guidelines on bike lighting. However, now that he has moved into selling lights as well as testing them, he too must be considered to have a vested interest. I was happy to buy from him 'cos I found his reasoning about lights agreed with my experience and other research I had done. (You can find his lights on eBay
. When I dealt with him he was the quickest, most efficient retailer I'd ever dealt with.)
6. Finally. I first used hub dynamo driven lights in the mid-1970s. The hubs were far heavier than today's and the lights more or less ludicrously dim unless you mounted them on the front drop out. But the battery lights of that era were even cruder. (Altho' I liked the ones you could attach on your arms or beside your knees--they could be seen through 270deg; I think MAFAC made them.) It's great that with newer technology and proper guidelines hub driven lights are now a viable, if initially expensive, alternative.