Player ratings vs Ability

Always been slightly confused with these 2 things on GS. Should I be looking at players with a higher PA or a higher Potential % rating??
Example
2 players in my current squad, both regens.

de Beek > ca 168, pa 180 best pot positional rating 81.16% as DC

Renato > ca 170 pa 187 best positional rating 78.81% as DC

So why is player with lower PA and lower CA rated higher in his best position rating????

Rating is more important because it's a reflection of how good the player really is (or can be, in case of potential). Ability is just an indication of possibilities, but rating shows the player's quality in relation to his positions and roles (which means taking into consideration the attributes that matter the most for them).
In your example, de Beek is slightly better than Renato.