you also need to distinguish whether you are talking about the frame or the derailleur. I believe CPcyclist is suggesting that you buy a braze on FD, and the appropriate size clamp to put on a frame without a braze on for the FD. I think this makes sense and it's what I have on my 2 road bikes.

If we're talking frame choices, all else being equal, I would prefer not to have a braze on for the FD. One reason being that if you go compact, it may be difficult to get the FD at the right height with a braze on. Without a braze on, the FD, or the clamp for a braze on FD can always be moved to the right height.