in Revised, the Allies win
in AA50, the Axis win
that, and you get a bigger board, more units that are more balanced and have a better price structure, Italy and China are included, although if you have 6 or 7 players I think those 2 guys would get bored and possibly angry from having to play their pitiful nations
if you are on a budget, or if you want a quicker game, you could just buy Revised but adopt some of the rules from AA50.
You could adopt the AA50 Tech Tree and Researcher tokens rules for example, though you would have to modify the Super Subs and Improved Shipyards to reflect the difference between AA50 and Revised.
You could adopt the new rules for Strategic Bombing Raids.
I don’t think those above 2 would change the revised game much, you could also adopt the new unit specs and prices, though this will definitely change the sea part of the game a lot. You could even make up your own national objectives or haphazardly create an Italian player with a marker or some paint on a few pieces.