I built my own, using a 20-watt low beam (energy-saver 35-watt equiv.) and a 35-watt high beam (energy-saver 50-watt equiv.) They are both 8-deg. narrow spots.

Narrow spots focus as much light as possible where you need it most. With the lower capacity of bicycle light batteries due to lighter weight requirements, you need all the light you can muster. IMHO.

Of course, I'm not familiar with off-road requirements.