Depends on the patient and the therapist. If I have a lot of money and several therapists available and not a serious mental health issue, then I have all the power. If I'm strapped for cash, if I have a serious mental health issue, if there is only one therapist who is willing to accept lower payment or lives close enough or has the time to fit me in, then s/he has much more power. There is no need to convince yourself that you have all the power if you don't in reality.

Sometimes there are imbalances of power in life. Sometimes we need to trust someone. When you are unconscious under the hands of a surgeon, you have very little power. At least nothing immediately (you or your family can sue the guy later if he makes makes a blatant error). Issues of power come up very often in therapy. Some patients and even sometimes the therapists too try to deny it. Sure, it may be that you're mistaken and you have more power than you have assumed. Or may not be the case. Regardless I think it's useful to think about it.

Also, to say someone has more power, may be very much context dependent. A psychiatrist might have the power to commit someone against their will. But the same psychiatrist might feel quite powerless when his/her car breaks down one night while on vacation and is at the mercy of some crook of a mechanic.

There is also the issue of if the power is legit. A good therapist having power is fine to me. Imagine dealing with a bitter secretary though. Like if you're applying for a job and are a little short with her, she will throw your resume in the trash. These kinds of people who feel powerless and bitter are the worst. They will make your life miserable. They will not let you forget that they have power over you.