I bought my first Mustang in October, 1964, and my last (a 65 CIJ Reissue) about a month ago. I played the first for almost twenty years befor I let some guy talk me out of it. I had gotten pretty much into telecasters by then.
But to compare the two. The pickups sound very authentic. I play D'Adario 10's now, which were not available in the early sixties, and they really light the Mustang up. The vibrato is still something to be handled with care and the "fit & finish" on the CIJ is immaculate. I was able to get the action and intonation set in under an hour (with the original Fender strings) and have not had to make any adjustments since. Personally, I have played and owned several CIJ models (usually tele's). I find the electronics to be different in several ways, but always functional and maybe more durable than the American counter-parts. For example, the pick-up switches in my new guitar have already proven to be much more reliable than those that came on the original '64. I was always hitting those original switches with contact cleaner from the first week that I owned the guitar. Incidetally, I paid $189 for that first Mustang (case included). I could have gotten the tele sitting next to it for $186 (again case included).
I would love to find the old Mustang because it was a great guitar, and the new one reminds me of how much fun I had playing the old one. Be careful in your shopping (for either the vintage or the re-issue) and either one could be your favorite in no time.