What types of jobs, schools, cultural opportunities, etc. are you looking for???
I think job opportunities, weight against cost of living, might end up being the biggest factor???
As far as NJ and FL(disney) Knoxville is at an excellent location, on I75 and I40.
Nashville, though, could still be a good location based on how you look at it.
It is about a 3 hour drive between Nashville and Knoxville.
Nashville is definitely a true metropolitan area.
Knoxville, while it has a pretty large populalation, would be considered by many to be more of a smaller city/town experience.
The most upscale and growing part of Knoxville... (with leaps and bounds!) is the West Knoxville - Farragut area. Tons of major development with shopping, restaurants, banks, hospitals, etc. have been going on at the area known as Turkey Creek. (maybe you could goodgle or yahoo that and see if anything comes up?)
Another area right outside of Knoxville that you could look at is Maryville.
I would suggest that.
Tennessee also has different geographical areas.
In the summer, Nashville will be very hot.... there are not many Tennessee hills there at all. Knoxville is on the foothills of the Smoky Mountains. Generally, not quite as hot, but still up in the 90's, and not quite as dry... (of course, generalities here)
It has been a long while, but I used to live outside of Knoxville... I may be able to answer questions if you wish to PM me.
I would start out by visiting websights about both areas.
And, of course, the only way to really get a feel for an area is to visit for couple or three days!
Hope this helps!