Best city in Tennessee? Surely you know the answers you're going to get, so why bother asking?
The Memphians will say "Memphis".* The Nashvillians will say "Nashville". The Knoxvillians will vote for Knoxville, and the Chattanoogans will vote for Chattanooga.
Good luck with your decision! (You may want to get the input of traveling ladies who've come to Tennessee; they'll probably have a more objective assessment of the cities here than us hobbyists, who'll pull for our own local areas.)
Cheers,
bcg
*Well, all the Memphians except for me; I'm kinda sour on Memphis as a hobby haven myself. But then again, I've never identified as a Memphian even though I've lived here 14 years come April; I've always thought of myself as a St. Louisan in exile. But we're not discussing Missouri here, so...