Not much. F|H servers stand in europe and WaW in america.
Well, our server is UK based to have good ping for both Europe and North America.
Also:
- different battle day (FHT: Friday, WaW: Saturday)
- we are focused on historical accuracy with divisions, regiments, battles and storyline
- we play 6h long intensive battle in 2 servers (less waiting rooms), they play 11h battles
- our map design standards are different
- we have different software than they do, our custom software (for medals, campaign tracking, army/company admin panel, etc) is being updated and improved monthly. I can't say how it is in WaW
- we have good experience organizing events for FH2 community, we are players, it's maintained by players (no companies behind) and it is for players
I suggest you to try both, they are free so it's not a big deal
Then stay which you like most