There's a lot variety in cocktail shapes out there. In my part of the world, we're much closer to Japan and almost never saw the classic "Ms Pac" cocktail shape in the wild.
Some types of cocktail make much more sense for rotation than others, and yes, it definitely matters what controls you want to have, and whether you're happy, for instance, playing Centipede with a trackball that by necessity lives on your horizontal side.
Don't rule out swappable control panels as an alternative to rotating monitor for a cocktail, either, depending on the shape and style you're considering, and how many games you think you'll need to support. The only thing I would suggest is drawing the line at games that need lightguns. Although it would look kinda funny to watch someone playing like that, shooting at their feet.
Follow the link in my sig and have a look at what I've just done, anyway.