First of all, the disclaimer:
Generally speaking . . .
Collectors regard Fender and Gibson guitars as 'real vintage' if they are pre late 1965.
Leo sold out to CBS in January of '65, so even a post Jan '65 Fender is still okay as they used up the stockpile of parts during the year. It's more to do with the features and condition than the date. A general rule of thumb is the small headstock strat is the one to have - but a mint large headstock custom colour from '66 will be worth more than the small headstock refinished 'hoss' from '65. A late 60's four-bolt neck is still a fine guitar - ask Bonnie Raitt.
Gibson made some significant changes in the same time period - notably changed the headstock angle from 17 degrees to 14 degrees and changing teh hardware from nickel to chrome plating.
But there are several changes pre-65 that also need to be noted. EG The early '61 and into '62 Gibson electrics have wide flat necks - they're just wonderful. Once you get to '63, they narrow out quite a lot - for me, not so cool. The '59 and into '60 Strats have a really nice wide (ish) flat rosewood 'board, so they work really well, too.
As for new vintage . . .
I think the early 80's dot-neck re-issues, the 30th Anniversary Goldtop Les Paul and the Heritage LP re-issues from the same period are probably turning into the 'new vintage' for Gibsons.
Fenders from the period are pretty weak. The 'American Strats' (with the jack on teh scratchplate) are pretty much a dog. The guitars withthe weird pickups (can't remember what they were called) had really bad bridges - and the pickups needed help, too. On the plus side, I saw several really nice '57 and '62 re-issue Strats that were good. I'm sure by now if you find one that's been played for 20 years, you'll have a real fine piece.