Spoke reflectors definitely trump reflective tape on the frame as, though the tape may be brighter, the unique circular motion of the spoke reflectors really draws attention from drivers (at least that's my experience driving), and from angles where spoke reflectors are visible it's almost always the first thing I notice about a cyclist... the light moving around in such an exotic pattern is hard to not pay attention to, and that's a good thing.

That said, I might take the liberty of some reflective tape on my rim (disc)... that might work better.