I'm biased of course but Chicago's nice. It's big enough that you can still get lost or see new neighbourhoods even after 6 years and yet you can get a good grip on the city. Living in the city itself is affordable and you can survive on a decent slave wage. It's a working class city.

Plus Mayor Daley is behind the biking and there's a lot of that here.

Never been to Boston so I can't compare but I don't find Chicago traffic all that bad.