As others have said, you'll get triple or quadruple your money's worth on NWN1+XPs in truly excellent mods. I played the game on a number of persistant worlds and solo for a long time, and the quantity of content available for it is excellent.

Don't forget that NWN2 comes with SecuRom too, which is why I don't own it and have only played it a bit on a friend's box.