One is a weak player, runs out of stamina can't defend and has barely played couple of good games this season. The other hasn't been himself at Milan for a while now and can't see him adapting to 4-4-2 our style.
To me 32 isn't old. My problem with Pirlo's transfer is not the age, my problem with him is that he hasn't been the same for a while now and I'm not into his playing style.