If it's daytime, I'm flashing both front and rear. On the front, even a small flashing light, like a Blackburn Flea, has significantly reduced the incidence of motorists turning in front of me. The slightly larger Performance Axiom (rebranded Moon) has more reach. Once it's dark, I run just a steady front light (a bright Light & Motion), but at dusk I run them them both, and keep the steady light on low so it doesn't wash out the flashing one.

I like to have two lights in the rear: a flashing light to get noticed and a steady one to be localizable. (I don't bother with the steady one during daylight, which means that when it gets dark I always have at least one rear light with a full charge.) In theory, my DiNotte Quad should serve both purposes, because the flash runs on top of a steady illumination. In practice, I think the DiNotte flash is just too bright at night, so I run the DiNotte in steady mode on my seatpost, and an Axiom 60 in flashing mode down low on my seat stay. In that position, it's very visible from afar, but doesn't blind people as they are passing me.