A mishandled and heavily outdated T-72 won't fair very well against any opponent; the T-72 series, if kept up to date and is handled by well trained and skilled professionals, will perform extremely well against any opponent.
A mishandled tank of any kind is not going to fair very well against any opponents. A T-72 in the hand of very well trained soldiers would give Leo 2 a fight of its life... might not win, but the battle can be hell to the Leo 2. In WWII, the germans had technologically superior tank to the Russian force, but in the end, the Russian gave hell to the germans.
Leo 2 and T-90 no doubt are good tanks, but they are not invincible... plus T-90 being a variant of T-72, might also share some of the weaknesses of T-72, thus when faring against Leo 2, they might stand at an disadvantage.
Leo 2 on the other hand is being used by Chile already and so Chile had more experience with that tank... they might even know some operational or tactical disadvantage of Leo 2 so by buying Leo 2, Peru had an disadvantage against the Chileans.
Finally Chinese Tanks are quite new to both Chileans and Peru... however Peru had the advantage due to the fact that they actually used Russian tanks before, and although VT-1A might not be based on the old russian tanks, the Chinese operating procedure are still quite similar to the Russian's so it is easier to get a hand on.
Plus like I say before, no one know what is the actual package that the Chinese wanted to sell Peru... we couldn't just see the tank as individual unit. The package might include license to build, technology transfer, etc.