I'm among the small minority that actually likes CDG for transfers, so that would be my choice, especially since it gives you the 777. My one flight through Milan (to Belgrade, actually) was a very unpleasant affair due to one of the frequent Italian ATC strikes.
For general info on Belgrade, try this recent article from the International Herald Tribune. If you have any further questions, PM me (I lived there for a number of years in the 90s).