Hypnotist has quite a lot of special content if you plant Triggers into people. Elsa got like 4 different repeatable scenes, plus 1 non repeatable ones. Plus you can invoke her trigger in her normal content as well from time to time(sometimes automatically) so it changes it there as well. And if you would be interested in watersports content, that is the only way to get Elsa into it...and that is also kinda hidden.
Hypnotist might be the choice with the most unique content. But, as people said, if you play it without cheating you might lose out on the general content. You have to use hypnosis nearly every week to get the Trigger to work. The reward can be pretty great though or even quite disturbing. Really is your choice how you do it. You could in theory only use it to improve and help people...besides of course forcing women to show their breasts all the time. But other than that, nothing is enforced. But damn, you can be downright evil.
Playboy does not much unique content, besides getting Rae as an exclusive Girlfriend(Hypnotist can do that as well, but again, more evil), a few different flavour texts and a handful of exclusive scenes. The principal for example really loves the playboy. If you want femdom content, he might be one of the best choices for it. But Playboy makes it *much* easier to get the desire up and seduce your clients during or after the training. At least I find him to be the easiest to play. Hypnotist really needs a specific playstyle, and not every client really needs Submission down for the Natural Dom to work as well. Desire is universal.