Well despite what the others have said if it's a big discount I'd buy the FFG one. Artwork is exactly the same and the errata are mostly relatively minor text changes. It hasn't affected my playing of it at all. But if the kosmos version isn't much more then buy that one.
It was a FLGS and the difference was $23. I lost out because someone purchased it before I could get there. I got stuck at work and was not able to get back to the shop on time before someone else purchased it
I will pick up the Kosmos version for my Bday in May given I am not saving anything right now.