i am just wondering what the differnce is between the two?
braze on attaches to your bike with bolts in bosses like a water bottle cage, clamp on uses a clamp that wraps around the seat tube.
like bruiser said. depends on seat tube. if it has a little tab sticking out it takes the braze-on FD. If not, then you need a circular clamp that attaches FD to seat-tube (check tube size first). Not your choice - depends on frame mfr.
Deetsay00,
Perhaps your asking about the front deraileur and how it is attached to a bike. A clamp-on attaches just like it sounds, by a clamp around the seat tube. This type of attachment affords easy adjustment of the deraileur as well as permitting it to be slightly turned, rotated on the seat tube, out of the chain line, not parallel, to assist shifting. Braise-on derailear hangers are more commonly used where seat tube shape does not afford easy clamping. Tubes that are not round or are so big around that clamping is impractical. As far as is one style better than the other or preferable? No, not really. They both work well and without both types, frame design would be greatly limited.