The most effective light I can recommend from my 15 years of urban bike commuting isn't a bike specific light at all. I use a fairly cheap set of front bar light and rear flasher but for riding thru dense traffic with lots of random light pollution from retail windows and such I've taken to dangling under my saddle a low cost LED flashlight set to strobe . This illuminates my frame and my furiously peddling legs and is visually disruptive in the idea way for making an impression on cell phone distracted drivers. People have commented so I'm pretty sure it doing the job - that and still being alive and uninjured. Gotta switch it off on the dark back streets of course because its strength is its weakness, its damned annoying.