I've tried both this year and I have to favor the reflectors for thier durability. Although the tape is good in theory to be able to wrap around parts and use with more flexibility, it just hasn't stood up to use (already cracking and peeling especially when it rounds corners). I tried a diferent type of sticky reflector too, works like tape, is precut in rounded rectangles and circles (from auto parts store), and it has stood up better but once again doesn't take to sticking well on anything except flat surface in my experience. I tried the rounded rectangle shape on my rounded fenders and it is starting to raise (peel up) along its edges.
might depend on the type of riding your are doing too. If your competing/training and want to put the time and money into replacing tape then go for it. Or if you are doing extended trips (like in backpacking) where wight is a concern. For me as a commuter, I don't see anything better than classic reflectors.