Although I've run marginally faster at Columbus than at Chicago (2:18:54 versus 2:19:31), I would think that PR chances are generally better at Chicago. I would also think that, as a sub-3-hour marathoner, you will not have to deal with the mass of mid-packers for any substantial length of time, regardless of which race you run (although you'll probably lose a few seconds at the start in Chicago).
Still, I would consider the advantages (and, perhaps, disadvantages) of running in your hometown. Avoiding the hassles of travel, having friends along the course shouting out encouragement, knowing the twists and turns of the course -- all of these militate in favor of Columbus. On the flip side, an out-of-town race can seem more "special," and the travel may give you a chance to get away from some of the day-to-day hassles of home life.
Based on my own very limited experience, my impression is that they are both excellent races.