The automatic is torque converter, so less likely to give trouble. The manual will eventually need a clutch, but maybe not until 100,000 miles or more. Manuals are significantly cheaper to buy than autos, but also have to be cheaper to sell, so you don't lose or gain. Depends whether you prefer driving a manual. I'd rather have one. But women generally prefer autos, and they are the main market for SLKs.