And only recently I’ve thought that in SW, Vader answers to Tarkin, In ESB, EVERYONE answers to Vader, and in Jedi, Vader answers to the Emperor. Just something that crossed my mind.
I think the comparison isn’t completely fair between the films. In SW Tarkin and Vader seem to be friends who respect each other but Tarkin is the military boss who is in charge of the station. Also Vader doesn’t have much to do really on his own.
That’s obviously the current retconned explanation. But when Leia meets Tarkin for the first time, she says that he is the one “holding Vader’s leash,” heavily implying that Tarkin was actually supposed to be Vader’s superior before ESB retconned it. It’s not too much of a contradiction though.