First Age
Explorer
There is! Behold, Monster Manual 3 on a business card.
They are meaningfully different, but it's not like it's a total ground-up rewrite. Accuracy penalties and bonuses were largely eliminated, damage was increased around 30% to 40%, hit points were often decreased (sometimes significantly), and in general effects were focused so they'd happen regardless of whether the monster succeeds rather than solely if it does (so that it didn't matter if any given monster only lasted 2 rounds, it'd still get SOME effect off and shift the flow of battle.)
All sorted now and with Monster Vault and the guidance I can gauge the numbers. Useful to get this clear before I move into actual play. Exciting.
Cheers.