I guess, the feudal lord (German: Lehensherr) would be played more often to have a chance for better buildings.
I've played only two games so far. And only read the rules after the second game (trusted the person who taught me the game the first time around). So we played incorrectly and replaced an empty building space immediately after a building was purchased.
I think with the correct rules (fill empty building spaces at the end of the round) makes the Feudal Lord more powerful. And it makes buying building more challenging - requiring more planning and better tracking of the available resources of your opponents.