D80 is a faster rubber (slightly flatter trajectory) so it supports speed with shorter stroke mechanics. It is also in a related way is more direct so punching and blocking is easier. But these are all subtle things that may be slightly different from player to player. Looping with the forehand against backspin usually has a different dynamic from looping with the backhand so some of this is approach dependent.
I actually place speed and the ability to block at a premium so I prefer the speed of D80 in supporting fast topspins at medium effort to the overwhelming spin of D05 on strong shots.
BTW, Takkyu's blade is one of the fastest there is with very low dwell so it is quite logical that D80 would be bit much with that blade on the forehand.
tbh the difference is not that big between D05 and D80. in a blind test i wouldn't make the difference probably... its also that ive been playing with D80 for much longer. before D05 i had T80 while i had already switched to the D80 for BH.
its always a good thing to have different rubbers on each side. you're giving a bit of variation to the opponent.
why do i like the setup ?
my blade is very fast. its easy to generate power and spin with very compact strokes, or even just the wrist if the incoming ball has enough momentum.
but in the short game, there is a good feeling.
serve is much easier than with slower setup.