Clamp on FD vs Braze-on with Clamp Adapter

A while back I had posted a question asking if my 31.8 clamp-on FD could be converted to a 34.9 clamp. Since it can't, I put in an order for a new FD and I asked for the 34.9 clamp size. When I went to pick it up, what the guy actually had for me was a braze-on FD with a 34.9 clamp adapter.

When I pointed out that I'd just wanted the clamp-on, he told me that this is a better setup overall...something to the effect that if the derailleur ever gets stressed, it will break off of the adapter, whereas with a clamp-on that could damage your frame, or something like that. I'm wondering if there's any truth to this, or if he's just making up a CYA story because he got the wrong one. To me it would seem like the only benefit of doing it this way is that I'd be able to put it on a different frame if I wanted later on, but I'm not too worried about that. The adapter seems like extra weight and extra complexity to me.

I'm hoping those of you who know your stuff w.r.t. componentry can weigh in and let me know if I should insist he get the clamp-on style or if the braze-on with clamp adapter is indeed a better way to go.

Thanks!

When I crashed my CF bike early last year and toasted it :( I got a crash-replacement frame and moved my parts over. The frame was a step up from my previous, and the seat-tube size was different. However, as the rear derailleur (a Dura-Ace) is braze-on, used with a clamp, the shop just replaced the clamp with a spiffy CF one for a fraction of the price of another Dura-Ace derailleur. So I prefer to go that way. I think it beats getting the derailleur in a big clamp size and using shims, or not being able to move the part to a new frame.

Functionally I don't see a difference so it's a no-loss situation.