I own a 75RI and have played the 50th ANV...
Damn it's a hard choice....I mean, seriously!
I absolutely LOVE my 75...it's my "go to" Jazz and I wouldn't give her up for anything....but the 50th ANV plays (if not exactly) very nearly as well....(IMO)
That is one choice I would really have to consider closely...
I would hate to be in your shoes and I would LOVE to be in your shoes!
Good luck in your decision! I really doubt that you would go wrong with EITHER choice!