Well, it is quite variable from time to time.
Better you just join the lobby an see yourself.
For example, as now, counting all games in progress with 2 or more players inside (some might be not really in progress):
1x Big World 2
1x Big World
1x New World Order
3x World At War
1x WWII Europe
3x WWII Global
5x WWII Revised
Lately prastle accounts for the majority of the WWIIv3 games played, maybe. It is not as popular as it used to be. Normally I see more game of the Big World v3 Rules mod than v3 itself.