Psychiatrists are medical doctors by training/education who focus on psychological ("psychiatric") issues and conditions, while psychotherapeutic psychologists are not medical doctors and are specialists in helping people with psychological issues/problems....
My own view or opinion is that psychologists of the psychotherapeutic variety are more likely to be helpful than psychiatrists, generally. Psychiatrists are too often oriented toward the pill (drugs) as a solution to everything. There are some good psychiatrists who are also good psychologists and who don't see drugs as the primary focus of treatment, but there aren't nearly enough of these around.
Drugs may sometimes be necessary or useful, especially in the case of severe and high-risk conditions like clinical depression with suicidal yada-yada, or bipolar disorder, etc. So, I'm not all against the use of drugs for folks with psych issues. But I think the psychiatric profession is too quick to hand their patients a prescription and a bottle of pills -- and that this isn't good. Be wary.