I've got the Airbike light and the DX Bike light, and there are noticable differences, quite apart from the price. The Airbike has a very diffuse, 'flood' beam, with little discernable centre spot. The DX has a definite centre spot with diffuse outer halo, which is much better for trail riding. I've found the light settings on the DX to be OK, the lower setting perfectly adequate for riding local trails. And the 'SOS' is nothing of the sort, it's a standard flashing mode useful for urban commuting or road riding in dim light. I went out for an evening ride last week with the DX's on, got around five miles into the ride and cars were lighting up. Connected up and got a red indicator light. Futtocks! Stuck the lights on flash, carried on riding. Got to the pub, around four miles, had a pint, got to the next pub, in Lacock, had another pint. Put the light on low, rode five miles home on low, more than enough light for the Sustrans towpath from Lacock to Chippenham in the dark. Sure, you might not be able to DH with the low setting, but honestly, for the kind of riding most cyclists do the DX is as good as you could want, especially for the money.