Hypnosis for personal development, and not for a stage show, may be better if you can do it by yourself. (It would be very difficult to hypnotize or mesmerize yourself or another person for a stage show).
Self hypnosis can be more difficult and take longer than being hypnotized by a professional hypnotist. In some cases, however, it may be easier – you may be more willing to be relaxed and trusting of yourself than of another person.
Another advantage is that for a long term effect, it may be necessary to be hypnotized more than once or twice. It can be more convenient to learn to hypnotize yourself than to have to go to another person.
It may take longer to learn to hypnotize yourself than to be hypnotized by a professional hypnotist, but learning to hypnotize yourself also removes any risk of spending a lot of money on an inferior hypnotist who perhaps might not get what you need done.
For therapeutic purposes, hypnosis with a professional may be superior, but it may not be superior enough to outweigh the risks and loss of control. Hypnosis can also be more beneficial if it is done regularly, and regular sessions with a professional can be costly.
There is also the risk of choosing an incompetent hypnotherapist, or perhaps one who already has their own theories of what you need to do. Some hypnotherapists can be very focused on repressed memories, and while these can surface naturally, and it may be helpful to have professional assistance should they arise, if a therapist is looking for repressed memories, they will find them. Even if these memories didn’t actually happen, because the subconscious mind is so receptive, it can be convinced something did happen.
For many people, a concern is that hypnosis will bring up repressed memories that they may not be ready to deal with, and for these people, it may be better to go with a professional hypnotherapist, so as to have professional help with any problems which may arise. You may also decide that it is less likely for you to bring back a repressed memory if you focus on your own goals during self-hypnosis, and thus this will not be a concern for you.
The natural advantage to self-hypnosis is that you can do this by yourself every day, which will more easily reinforce your goal and may make success more likely. This advantage may outweigh the advantage to going to a professional therapist or hypnotherapist, who may be better at hypnotizing you, and get faster results, but would not be able to provide the desired daily long term benefits.