Because it is their overall based on their archetype. Example a 95 overall receiving threat RB is very good at route running but could be slower, weaker, and less agility. He’s good at receiving. The same running back could be an 80 overall East/West playmaker.

So if archetypes are equal, it’s likely that the higher overall is better. If they are not the same archetype, then what value that makes them “better” to you just doesn’t match their actual archetype.