Hey guys  yearsa go I bought RainbowSixVegas 1 and 2  for PC it was the normal retail version. Then years later the game was released on Steam. And my buffy wants to buy the game on steam now.

The problem is  he wants me to buy it too otherwhise he wont do it.  I told him I already have the game but the problem is we dont know if both versions will be compatible.

Does anyone know if R6:V works when one guy has a steam version and the other one has the retail version? 
Is there a site out there that lists stuff like that? (like the sites that list languages in games etc...?)

Thanks for the help

That would entirely depend on whether the game uses Steam as it's online service like Age of Empires 2 or Team Fortress 2 or whether it doesn't use Steam as it's online service like the Call of Duty games. It should be mentioned in the description of the game on Steam :)

The games are released by Ubisoft who isn't exactly known for heavy Steam integration. It seems, judging by the games' Steam pages, that there is absolutely no Steam integration which would indicate that the Steam version doesn't use Steam's servers for multiplayer, ie. you should have no problem playing the game. I'm not entirely sure but I'm confident enough that I'd buy the game if I was interested in it. Besides, neither of the Vegas games is very expensive.