Both.
Psychologists are nice for helping you work out issues, especially if you can't talk about your problems with anyone else. Their effectiveness tends to dull over time, but don't let that stop you from seeing one. They're good at making life a little less hell-ish when you need it to. Great for accelerating understanding of world, self, etc.
Psychiatrists are all about the medicine, which not too many people really need. All it did for me was make me more self-conscious about depression... which for the record, didn't help. People with chemical deficiencies need medicine, for anyone else, medicine has a placebo effect at best.
Stopped seeing both in the end, didn't need medicine since it was more of a cognitive problem, and I had run out of crap to tell my psychologist. Didn't help anymore, so I just stopped. Psychologists have given me good ways to keep a good cognitive mentality, and although things aren't perfect, they've improved.
But I think what really matters most is just feeling loved. At least, for someone who keeps getting depressed by poor cognitive mentality. Love and other good feelings keep rumination in check.