Tbilisi is Georgia's cultural and historic heart, with a compact old town of sulfur bathhouses, balconied houses and hilltop fortresses that reward slow, walkable exploration. It also has the country's main international airport, which makes it the natural starting point for most itineraries.
Batumi, on the Black Sea coast, offers a completely different atmosphere, with a modern promenade, beaches and a skyline that mixes contemporary architecture with botanical gardens just outside the city. It suits travelers looking to relax after days of sightseeing elsewhere.
The two cities are connected by a comfortable train and highway route of around five to six hours, or a short domestic flight, so most visitors combine both rather than choosing one over the other.
If your trip is short, start in Tbilisi to cover the historic highlights and day trips to Mtskheta or Kazbegi, then add Batumi at the end of a longer itinerary as a coastal wind down before flying home.