Aguero can do something none of our strikers can do. DP used to but not anymore. He scores goals with either foot, both are deadly. He creates for himself unlike useless players like Amauri who for 3m a year supposedly needs "crosses" to be effective, his touch is infinitely more valuable than a hee-haw IQ's, as deadly in front of goal as Trez, and a wizard with the ball from all areas of the attack like DP used to be.
If ever there was a player on this planet to adequately fill the shoes of Alessandro Del Piero this is the guy. I challenge anyone to propose someone else better without considering money for a change.
I'm telling you guys, in a 442 he will be ten times more deadly than Diego so keeping Diego as another shot shouldn't be the problem, its a matter of who will bring this team more glory and end product. I'd like to keep Diego as well but any sane person will tell you that if the chance arose to sign Kun and is passed up then a grave mistake was made.