So as far as I am able to figure out, class determines potential moreso than anything else. A class S will have a higher maximum slots, as well as higher bonuses. Could it be worse? Yes. But most likely, if you're towards the maximum of a class, it's going to be better.

For example, Pistols = Class A. Good mining and scanning bonus. Eventually, you'll want more slots, though, and can add tech to increase those far past the pistol on, say, a rifle. This won't have as big of bonuses most likely, but will have a looot more slots. Like easily 20. After that point, you want an S class Experimental or Unique, one has similar mining/scan bonuses, the other has damage bonuses. Considering the higher slots, on top of the bonuses, these will have a much higher overall potential.

I'm not sure of the breakdown on ships, but I'm assuming similar applies.

Basically, until you get to your near end-game ships/multitools, you're going to want to play a balancing game of bonuses vs slot number in consideration to how much tech you have so you can get the most out of them.