Squad Battles ,which one ?

[nukkxx]

Hello everybody, this is my first post here :-)

I have a simple question: which JTS squad battle should I purchase ? 

Soviet-Afghan War 
or 
Modern War

My main concern here will be to easily find PBEM opponents. 
But of course, the quality of the game is important but it seems to me that all JT titles are great ... 
  
Anyway, which one should I buy ? Or maybe there's another squad title that is a must have before any of these two ?

Thank you in advance for your help !