Lurking underneath the Japanese sheetmetal lurks a distinctly German heart. Platform sharing, badge engineering, throwing in the towel-call it what you will, but this Infiniti is a Mercedes-Benz GLA250. Or is it? This particular model is the QX30S, a sportier derivative of the small, premium SUV. Besides the looks, how is the QX30S different from the Benz? Is it better? Is it faster than some old supercar? What does Randy Pobst think? Most important of all, should you buy one?