I think Cincinnati, OH, would have to be my top choice. Idlewild, Banklick, Mt. Airy, and tons of other courses. According to the DGCR search engine, there are 150 courses within 150 miles of Cincinnati, and 50+ are rated 3.5 stars or higher. Other major metro areas within that distance include Indianapolis, Columbus, Lexington, Dayton, and Lexington-Fayette -- all with their own disc golf scenes. For big tourneys, you can get to St. Louis (5.5 hours), Kalamazoo, MI (5 hours), Ann Arbor, MI (4 hours), Pittsburgh, PA (5 hours), Bowling Green (3 hours), Nashville (4 hours), and a host of other cities.
Charlotte, NC, might be my runner up, for reasons -Dut- gave. Renny Gold is my favorite course I've ever played, and Charlotte weather is mild enough to play pretty much year round in sunshine. Lots of good tourneys in Raleigh/Durham, Augusta, Winthrop. Ashville is beautiful...
And, in a five-way tie for third:
Allentown, PA -- several amazing courses that hosted worlds, and lots more amazing courses within a short drive.
Pittsburgh, PA -- Three of the top 20 courses in the country in that area, and several more on the way. Very enthusiastic locals.
Portland, OR -- just be a great city to live in, and some amazing disc golf. Look at the OR courses: three of the top 10.
Austin, TX -- lots of above average courses, and you can play there year round, which is worth a lot. And courses keep improving in TX.
St. Louis, MO -- It would just be great to spend time with Dave and the Gateway folks; I think it would be a chance to spend a lot of course time with some amazing players as well as look behind the scenes at more of the disc golf business side of things. Also, some great courses, and close to Kansas City and other big tourneys.