Allowing a brief digression, if we were to compare AA50 to AA42, we find AA50 adds:More board spaces
[liA nicer looking larger board[/li]An additional power Better rules for China Cool new factors such as NOs and technology
AA50 is a better game with more bells and whistles, but some might prefer the relative speed and simplicity AA42 has to offer.
Back to the topic at hand, if we were to compare AA50 to AAG40, we find AAG40 adds:
More board spaces
A nicer looking larger board
Much better rules for China
Cool new factors such as Politics, bases, neutrals, and convoy disruption
Tactical bombers and mechanised infantry
New rules for ICs
expanded rules for 2 hit warships
AAG40 has more features above and beyond AA50 than AA50 has over AA42. Some people still might prefer the relative speed and simplicity of AA50, but you have to decide if you think you’ll be one of them.
Me, I think AAG40 is the best A&A game ever! It obsoletes AA50 more than AA50 obsoletes AA42 (though all three are highly playable solid games).
One more thing, although AAG40 is new and optimal strategies are nowhere near having been refined, it looks like AAG40 has more viable strategic options than previous versions of the game.