The formula isn't really difficult, guys.
If you sign Doria and he manages 7.5 and Balanta avg 6.8 over a period of 10 years - Doria will be better.
If you sign Balanta and he manages 7.5 and Doria avg 6.8 over a period of 10 years - Balanta will be better.
There are other factors. Such as training, and loaning out, that change variables. But ultimately, anyone who actually knows the engine, will be able to tell you all these threads about "who is better" is kind of ******* useless and probably the main cause of why so many people have difficult playing the game and the "frustrations" thread is a bunch of people who haven't actually read the manual vs. the occasional person who has a genuine issue. So I don't feel sorry for people like that at all because they find a way to ruin it for everyone else because of their laziness/inability to grasp that unless you understand something you're most likely to continue failing at that thing.