About a 70 pound differance.
I just think that the 8.8 is not needed for most applications, but is swapped because its "cool".
If it makes money sense, then ya go for it. Such as swapping in a disc rear from a Turbo Coupe. But if you are happy with your gears and you already have a "posi" then there is no point in swapping. You will not go any faster , and the extra weight can only slow you down.