If flying to FL is high on your list, living closer to Nashville is a better choice. Knoxville is a decent little airport, but nothing like Nashville. That said, any of the 3 towns you listed should be fine.
Oak Ridge gets lots of bad weather and the cops are strict (as are the traffic cameras) but ORSA might make up for that. Proximity to Knoxville can be good or bad depending on your perspective.
Crossville gets its share of bad weather as well, along with more ice/snow in the winter due to being on the plateau, but its also a little cooler in the summer. It's much more "small town-ish" than Oak Ridge.
Athens has grown a lot over the years and I'd put it somewhere between Oak Ridge and Crossville.
That said, given the option I'd pick somewhere in the "far east". We used to live near Kingsport and really liked it there.