I think the comparisons and recommendations between Kingmaker and WotR are going to end up being the same as DOS1 and DOS2.

If you can only play one, pick the second game. Then pick up the first game afterwards if you are interested in seeing how everything started, and to compare and contrast the two games.

In the case of Kingmaker VS WotR, Kingmaker's gameplay pacing is basically main story -> downtime/exploration phase -> next chapter main story -> etc throughout most of the game. It has a somewhat open world structure too. WotR is a much more linear game with almost no downtime between each story beat, and also features a lot more proper dungeons and miniboss encounters as a result. Though while it is more linear and the game is said to be shorter overall, it also has more divergent path choices compared to Kingmaker.