You can't really compare them. But if you must, overall, Kingmaker is the best one, they really took a lot of care with it, for example they dropped the description of each monster from the in-game encyclopedia in Wrath... but Wrath has still things that are done better than in Kingmaker.
The mythic paths ensure a lot of replayability, and the implementation of epic level DND is decently done.
They are both solid on the setting and main plot. But companions are pretty meh.
Rogue Trader is OK, it is actually shorter than both the previous games, which is bad, but the setting is well done and so are the companions over all, it even has the best minigame of the three games, the space combat one is actually funny.
Main plot has issues towards the end, I think it was rushed out and they cut a big fat chunk.
The combat being turd based and super easy is unbearable, any fight forces you to lose 10 minutes, and since it is at the moment trivial even on the hardest difficulty, really feels like a chore. Even enjoying a lot the athmosphere I can't force myself to replay it with this combat, while in Wrath and Kingmaker I immediatly started a new game after I finished both. It was still enjoyable enough that I hope they can fix it so I can replay it and see the other paths, and will play the DLC(s) but Owlcat DLCs for the Pathfinder games were quite bad so I am a bit skeptic.
All in all, all three deserve to be played and Owlcat is nowaday the best CRPG maker on the market, nothing come close in the last few years.