This is a toughy. Well, considering Vince is probably the better, or more valuable player to the Nets at this point...plus the fact that Jefferson can be traded much easier, and bring back much more, I'd definitely rather trade Jefferson.
To add onto that, if Vince's play during the end of the season is any indication of what we'll see from him in coming years, I wouldn't be all that against keeping him on the team.
Of course, if we could find some good trade partners, I'd love to trade Vince AND RJ.