All four spare you the clutch pedal but drive differently. An AMT is a manual gearbox with a robot doing the clutch and shifts: cheapest and frugal, but with a pause and a nod at each upshift. A torque converter uses a fluid coupling and a set of gears: smooth and durable in traffic, slightly thirstier. A CVT uses a belt between two variable pulleys: the smoothest and very efficient in the city, but it drones when you accelerate hard. A DCT uses two clutches to pre-select gears: quick and efficient, but some versions hesitate or judder when crawling. For mostly city use on a budget an AMT works; for heavy traffic and long ownership a torque converter or CVT is the safe pick.