That depends on the kind of hypnotic suggestion you are aiming for, imo.
Spiral Eyes are good for a simple maniacal or trickster dom who wants to simply pull people into them.
Blank eyes (especially if they glow) have a more corruptive, manipulative magic tone to them that can be really hot at times. It's also pretty good for blank expressions for when applied to the one in a trance.
The Same could be said for Shadowy eyes, except with a more demonic or otherworldly vibe to them, which works well for demons aliens, etc.
Spiral is always super fun, it's a personal preference (easiest way to indicate hypnosis in a visual medium as well IMO) I especially like it when the spirals or rings in the eyes or out of sync, somehow makes it more enjoyable to look at!