Hiring a car gives you the flexibility to travel beyond Tbilisi and build a wider route through Georgia at your own pace. It makes it easier to combine places such as Mtskheta, Kazbegi, Kakheti, Kutaisi, Borjomi, Vardzia and Svaneti.
Having your own transport also gives you more freedom to stop at viewpoints, monasteries, villages and smaller towns along the way, rather than organising each journey around fixed transfers or tours.
The main decision is which vehicle suits your route. Many major roads are paved, while rougher mountain or remote routes may make extra ground clearance or a different vehicle type more useful.