I would say it depends on the conditions. I personally have two PB flashers and usually run them both on steady, like a car. I figure people are used to not running into cars so looking like one is a good thing. Although, thinking about that, a car's tail lights are placed much further apart which could cause a driver to think I am a car further away causing an accident. Enter pedal reflectors, they denote bicycle. If I had one light brighter than the other, it would be the one that flashes just because if I put a frog light flashing next to my PB flasher on steady, it would be like a strobe light next to the sun, you will never see it.
And that, is my 2 cents.