Quick answer
Marietta is the historic Cobb County seat — a walkable Square, an aerospace employment base, and its own independent school system, with median home values around $448,500. Kennesaw is the more affordable, college-town choice, home to Kennesaw State University, with median home values around $335,000. Both are in Cobb, both car-dependent with a 6% sales tax. Choose Marietta for history, the Square, and its city schools; Kennesaw for value and KSU.