I’m a fan of strobes for daylight-only city biking (where a) everyone’s pupils are already tiny and b) you don’t cause people to lose their night vision). The problem can be that the stroke always blinks at the highest lumen level. Some recent light have a set of alternate “walking mode” settings (requires you to hold the button for a while when turning on the light) one of which is a lower-power strobe for walker’s night use, which, might be acceptable for night-time city biking. Maybe.
Most of the time, I use my front headlight in lowest-power mode. Saves on battery and the current tech is usually 100-200 lumens or so on low.
I am the jerk who uses one of these on the rear of my bikes, mostly because I can set the LEDs to circle in a 360 degree sweep at night: http://www.amazon.com/Aervoe-1185-LED-Road-Flare/dp/B003GAXXUU
Brendan