How is psychotherapy with a psychiatrist different than with a psychologist ?

There is overlap: but psyciatrists these days primarily provide medication and monitor it while checking on your condition and progress. You may see them monthly or less. Clinical psychologists diagnose and treat mental illness and other common disorders and situations, not only illness. Their unique strength is diagnostic testing if needed. They do psychotherapy and meetings can be weekly, every other week.

It isn't: Psychiatrists who offer psychotherapy (not all do) are usually indistinguishable from psychologists offering the same therapy. Each discipline has other unique skills the other doesn't have. But psychotherapy can be done well by both. A bigger issue is what type of therapy is offered, and what is best for you personally.

Therapy vs meds: Speaking very generally, most psychologists hold either a PhD or a PsyD degree (I hold both) and practice psychotherapy. Psychiatrists hold either an MD or a DO degree, and they prescribe psychotropic medications, and generally do not do all that much therapy these days, but years ago psychiatrists would do both.