The Audi A8 is a formidable competitor. It flies under the radar, a sleek, tailored, capable machine that’s not flashy or ostentatious. Like the BMW 7 Series, it’s offered with eight- and twelve-cylinder engines, in short- and long-wheelbase body styles. Audi’s Multi-Media Interface (MMI) is less confusing to use than BMW’s iDrive, but is also less elegant in terms of appearance. Unlike BMW, Audi offers a performance-tuned S8 model, but that might change with the next-generation Seven.