I always purchase so I have the freedom to trade in whenever I choose. Generally after 1 or 2 years. If u can swing it, pay cash. It's always a good idea to avoid financing a depreciating asset.
Present: '14 S550, '13 Carrera 4S, '11 E550, '13 RAM 1500
Notable Past: '13 M5, '11 Range Rover Sport Supercharged, '08 CLS63 AMG