I live in Minnesota. My impression is that employee turnover is ~2-3x higher in coastal markets, which I'd expect to lead to (1) less willingness to obtain company-specific/business domain-specific expertise, (2) more fire drills/"we'll fix it later" syndrome as people leave at inopportune times, and (3) more resume-driven development, which in turn means more time spent working with unfamiliar and/or inappropriate frameworks. In terms of intelligence and coding ability there's probably about zero difference on average, but the environment here just seems more conducive to building quality stuff.

Ironically, a lot of the big employers around here still think dev salaries in Minnesota are too high and are increasingly squandering that advantage by bringing in contractors from H1B body shops instead of continuing to develop talent internally.