Cyp has an extra carbon atom so you'll get a shade less testosterone when you shoot cyp versus enan. This difference, though, is practically negligable. Cyp is also a shade harder to dissolve and, correspondingly, comes out of solution a shade easier. Accordingly, there's an increased chance of pain with cyp.
All in all, though, you could likely lose the labels off two vials of cyp and enan and neither know nor care which is which.