It depends which automatic. A torque converter diesel automatic makes sense because then there's no need for a dual mass flywheel. A VAG DSG or S-Matic or a Ford Powershift diesel auto, on the other hand, needs a dual mass flywheel to protect the box from torque reactions and that can be troublesome. A good CVT needs no DMF and can give excellent economy, but historically CVTs themselves have not been brilliantly reliable. Audi Multitronics and the CVT in the C-Max 1.6 diesel are cases in point. But Toyota has now gone
CVT in the IQ, Avensis and Verso as well as the Prius and Lexus hybrids. The more prestigious the car the more important an automatic box is to its resale value. A 5 Series BMW, an E Class Merc and an Audi A6 are worth less as used manuals than as autos, sometimes £3,000 less, so a bigger penalty than the extra cost of the autobox in the first place. If you go for an auto, though, it's essential to learn to left-foot brake while manoeuvring because you never know how much control you will have over the car with your right foot alone in a confined space.