High vis vests most of the time. Reflectivity can be on the vest and on the bike but it's the flourescent yellow/green that sticks out and helps define my shape during day, night, rain. I had a yellow Bellweather with mesh back that was perfect for hot weather but the zipper is blown out. Right now in the cold weather the vest I'm using is one of those flourescent yellow/green jackets with removable sleeves.
I'm exposed to the most traffic during the day/morning/dusk and that's when I've had most of my near misses when people simply don't see you even though the light levels are high enough that lights aren't needed or providing reflection.
You know the situation,car pulling out from parking lots with cell phone to head, turning left from the other lane across your path, cross traffic merging just as you're coming into the intersection. BRIGHT flourescent vest does a lot more good than reflective vest.