Another question is whether you like campaigns? The WW1 title has the most campaigns in any title if I am not mistaken (because I personally love them - the feeling of trying to set a LAP high score, and the feeling of progression). ;)
If you don't care about campaigns, then obviously this is a non-factor. Just saying.
As mentioned though, the bad thing about WW1 usually being the unit density and the level of carnage.
Personally, I like all three titles, being that they show off how one game engine/system can be totally different depending on time and conflict. SqB is certainly very robust.