Keep this one, delete the other one, I voted for the wrong one on that one and you can't change votes which I think you should be able to since I've often heard people misclicked.

I find it more fun with a different main villain each time, to get a glorious defeat at the end and then a new one come along.

This depends

I mean, of course, for whole series it has a bigger satisfaction factor when they are defeated like my two absolute favorite MVD's, Palpatine and Voldemort, and Sauron not far behind them. Same with Naraku as my fourth favorite anime MVD.

I like for one villain to have a constant presence throughout the story while other villains may have their own character arcs.