I am a newbie so my opinion shouldn't count for much but...
Since the lighter aluminum differential is "sprung" weight (attached to the frame) then it should not affect handling to any degree. You save some weight going from iron to aluminum but the weight savings is in the rear. Most cars are front heavy so weight savings in the rear is a +/- thing.
The other item is I believe the inner CV joint is a little stronger. I don't think you will notice this until/unless you break the joint. If it is strength that you want I believe the 1.5" Raxles are the way to go.