Everyone will have personal factors that dictate what area is most desirable for them. All other things being equal, however, would you rather live in a city that's a balmy 70 degrees year round with beautiful beaches, mountains, awesome restaurants, and music venues, or in a town in the middle of a million square miles of corn fields that's minus 20 degrees in the winter, and have one movie theater and an Applebee's for entertainment? There ya go.
Talking to a few graduating residents/fellows on the job hunt, it's generally pretty doable to get a job as a family medicine doctor, emergency medicine doctor, hospitalist, intensivist, or general cardiologist in "desirable locations." On the other hand, I've heard of cardiothoracic surgeons and neurosurgeons moving to the middle of nowhere for jobs. Nephrology is supposed to be really bad as well. The desirability of a location and how much you get paid there are often inversely related. The less doctors want to practice somewhere, the more hospitals are willing to pay to recruit them.