NONE of the blinkies are anywhere near as bright as a good reflector though. Best to have a bright blinky AND a good amount of reflective material. Most blinkies will not act as a reflector, so if you take your rear red reflector off to mount a blinky in its place (as many people do), you will have lost LOTS of visibility from the rear.

One of the few blinkies that offers rear light, side light and a good amount of rear reflector is the Busch & Müller "4DToplight Permanent". It's made to comply with the German standards which are far stricter than the US DOT / CPSC standards. I have one, and just ordered a Tubus Vega rack from The Touring Store that I'll be mounting it on.