Oh, okay, so the Prom R is actually a little more powerful than the Kayser, right? Because it's never directly presented in the game. I mean, it has observable empirical properties apparent in the game, but you'd have to open a table to figure them out.
No you don't. You use both weapons at once and it becomes rapidly obvious which is superior. You could conduct empirical testing on the matter without referring to FRED since the player has a choice of armaments.
Oh wait. The fire rate and turn rate of Shivan ships is directly presented in the game.
But there is no way to conduct empirical testing on it without reference to FRED. It's not possible to separate performance of ship and pilot without recourse to exterior sources because you cannot control such ships yourself to see what their maneuver limits are nor can you accurately assess which Shivan pilots are better or worse than others. At the very least, they're going to be attacking you. That makes observational evidence very dubious.
You can do it however you like, but since you never personally fly a Shivan ship or fire a Shivan weapon, without recourse to the tables or FRED you don't know what the basic limitations on them are so you can never assess how well they're being used. Without consulting the tables you can't even know if the AI is actually being gimped down from what it's at when played on Insane or whether Insane is actually it being buffed from norms established at Very Easy. There is no way to simply play FreeSpace or FreeSpace 2, alone, and accurately assess the capabilities of Shivan fighters. At best, you can talk about how they perform at a certain difficulty level. That doesn't tell you anything about how they're meant to be. You want to figure that out, you have to crack open the table files. And gameplay will always represent a higher form of canonicity for a game.
If anything, it seems more likely

intended us to walk away with the impression all Shivan pilots are idiots, based on Into The Lion's Den and what you accomplish using one of their ships. (Or alternately, that Shivan pilots are all gods, based on Playing Judas.)