Pokemon-go – Does CP determine the aggressiveness of a wild Pokemon

There are multiple.

The biggest one is that pokemon you evolve tend to have a higher CP than an already evolved pokemon in the wild but their maximum CP will always be the same. An exception would be if you evolved a pokemon when you're at level 5 but then you catch the same pokemon at level 10. Because your maximum CP for every pokemon is higher with trainer levels the pokemon you find also have higher CP.

The other reason is that you gain a fair amount of experience from evolving a pokemon. It is 500 experience per evolution and an extra 500 if the evolved pokemon is not something you have caught before.

It depends on how far into the game you are. Up until level 24 or so usually you only care about CP and if the CP are similar then the movesets. Once you get into the medium to high 20's that is when things start to get more interesting.

Outside of just movesets and CP there are also IVs (Individual Variables) to keep track of. A Pokemon's IV determines its maximum CP, CP per level, and health. However as long as the IV difference isn't too large, I believe moveset takes priority over IVs because it is more than enough to make up for the CP/HP difference a lot of the times. Another reason why at this point in the game you care a lot more about IVs is because you have a lot more stardust and can finally justify spending them.

Think of good IV pokemon as a long term investment while high CP pokemon as short term. It's really important to balance out the two. And if you follow the moveset chart you are good to go. Keep in mind that movesets are random after evolving so if you find a pre-evolved pokemon you only want to look at CP/IV because IV's are the same after evolution. Weight/size do not matter at all compared to these other statistics.

Best movesets for each pokemon can be found here. IV calculator can be found here.