Comfort, elegance and tasteful understatement - that's the DNA of luxury cars. Our two test models this week - the Mercedes CLS 350 and the Audi A7 Sportback - certainly embody all those attributes. The Audi A7 has sleek, classic lines. While it resembles a coupe, the Audi has a spacious feel to it - although as we discover, looks can be deceiving.The Mercedes CLS 350 has a more sporty image... emphasized by the thrusting grille and dynamic, wrap around headlights. We compare the two models - looking at aesthetic design, performance, space and the range of special features.