Single LED lights - advice from a motorcycle courier

IMO front lights are far far more important than rear lights. You are really unlikely to get hit from behind and much more likely to hit someone pulling out at a junction who didn't see you. it's all to do with time.

No it ain't, it's better to have a brighter front light, in the city too.

Maybe, but then again you've got eyes in the front of your head, so you can see and anticipate any hazards ahead of you. Those approaching you from behind are harder to spot.