I have tried many different bicycle lights over the years including:
1970's / 1980's
1) Eveready 2 "D" cell incandescent bulb lights.
Verdict: heavy, dim light and unreliable and expensive to run.
2) Eveready Nightrider 2 "D" cell incandescent bulbs, upgraded to halogen bulbs and industrial capacity "D" cells
Verdict: heavier, but better light and more reliable and after initial investment cost, cheaper to run.
3) Union tyre side-wall bottle dynamo + halogen light (at the front)
Verdict: lots of work to install, but quite good lights but lots of drag and dynamo roller kept slipping against the tyre in wet conditions
1990's
4) Vistalite first generation LED lights using 2 "AA" batteries
Verdict: better reliability, lighter, cheaper to run, but only suitable as see-me lights, not suitable for me to see where I am going.
2000's
5) Sturmey Arched Dynohub + halogen lights (also continued to use Vistalites as backup for dynamo)
Verdict: a lot of effort (and cost) to set up, pretty good lights (at least for that era), low drag, but occasionally blew halogen bulbs.
2010's
6) 3 bicycles fitted with more modern Shimano dynamo hubs and LED lights
and 1 bike fitted with Nordlicht bottle dynamo running against a tyre with dedicated dynamo running track on the side-wall which virtually eliminates slipping in the wet.
All 4 use Busch & Muller Toplight Line Plus rear LED lights
Verdict: very effective / visible and includes a good rear reflector too,
all mounted on the end of a rear rack on each bike.
6a) Schmidt E6 halogen (fitted to the bike with the Nordlicht dynamo)
Verdict: very good light, for a halogen light that is (LED are much better)
6b) SON Edelux LED headlight.
Verdict: a really well constructed light with good light output. I like the automatic light-sensor switching (although it is a bit conservative about what it considers to be low light so it is on quite a lot of the time on dull winter days). The only problem is it is far too expensive - very unmustachian.
6c) Busch&Muller Cyo T
Verdict: about 1/2 of the price of the Edelux and just as good a light output, also rather lighter (i.e. plastic rather than aluminium) construction. Also has light-sensor switching which works well.
6d) Philips Saferide LED *dynamo* light.
Verdict: Only a little more expensive than the Cyo, construction (apart from the too flexible mounting bracket) at least as good as the Cyo, but with an aluminium case which is a bit more solid but is also heavier. No light-sensor switching, which is a feature I miss a bit, but not that much.
7) As a backup for all 4 bicycles, I use a pair of Cateye Rapid 3 (front + rear), which are trivially moved between bicycles.
What would I buy again?
Answer: a dynamo hub, B&M Top Light Line Plus, Philips Saferide LED dynamo light and front and rear Cateye Rapid 3 as backup lighting.
Reason: this is currently the best of the various options out there (in the UK / Europe) that give very good light output (in an on-coming traffic friendly way) at a reasonable price point (for me that is) and a reasonable construction / manufacturing quality and in the last 3 years have provided utterly reliable lighting.
P.S. all the dynamo-powered lights provide a "stand-light" which keeps front and rear lights lit even when stationary for at least 4 minutes (nearly 10 minutes for the Philips Saferide).
(And 4 minutes seems longer than the original Eveready lights used to stay working for.)
Just my 2p worth
