Yes and no, "better" is very often subjective. It used to be the case that you could buy a professional quality vintage horn for much less than a professional quality new one, however the market is now opening up due in part to some very good and inexpensive saxophones being made in Taiwan and recently China. This may be the reason that Ebay prices of vintage saxophones seem to have dropped recently - there are now some bargains to be had, although it seems there will always be people who will pay inflated prices for a Selmer MKVI without even trying it out, only to find that the good ones do not get sold very often.
There are certain qualities that vintage classics such as the Conn "Naked Lady", Buescher 400, Buescher Aristocrat, King Super 20, Selmer SBA and the Selmer Mark VI have to offer that you cannot find in a modern horn. Even Selmer’s sad attempt to recreate the vintage horn with their Reference models has not dented the market prices of MK VIs.
Although there can often be more character to the feel and sound of a vintage saxophone, they rarely have the consistency of tone that you get with a modern instrument: there may be some notes that are a bit different in tone or tuning, but after playing for a while you compensate for this.
LINKS:
Saxquest - Vintage saxes and mouthpiecesSOTW Vintage Saxophones
Gayle Fredenburgh Vintage Sax
The Martin Story - site dedicated to the Martin saxophone
Cyber Sax
Edinburgh University Collection of Historical Musical Instruments
Some Vintage Buescher Advertisements:
Only a few months ago this boy was a social failure in his own home town. He was avoided, shunned by the boys and girls who should have been his friends and companions; because he was backward, uninteresting. He could not entertain. He had nothing to contribute to the fun. But now! What a difference. he's the center of attraction, everywhere. His school mates idolize him. No party is complete without Tom-Tom and his Buescher True-Tone Saxophone.