arenas is still young and can ball. carter is old and washed up. nelson will probably never develop into an all star point guard. if nelson can redefine his role into a passing/3pt shooting pg then arenas would fit right in. right now carter sucks in fourth quarter situations but arenas won't be shy.
dudes approaching 30 though. he missed most games the past 3 seasons due to the injury in his knee, so even though he's a bit younger than VC he won't be any more sustainable than the 33yr old vince carter. plus arenas has a bad history of igniting disharmony in the locker-room, which also counts against him as well.