WW1 has a very different feel, and it's an absolute blast, but it's also slower. The biggest thing about it is that when you move to attack a province you only roll once, as does the defender, and if there are units of both sides after the roll the province becomes contested, denying its resources to the defender. On their turn the defender can move units into the contested zone and counter-attack, and the process continues on and on. There's a lot more little differences here and there, but the core of it remains the same. If you're looking for something different, then WW1 is probably the best bet. The 1940 games are a lot more strategic and a good amount more complex, and though a blast (I've spent multiple weekends playing with 5 friends 1940 "global", where you combine both 1940's into a monstrously big single game) it's somewhat more hardcore due to having a good amount more micromanaging and planning ahead.