Audi S3 is a blast to drive with quick acceleration and sharp cornering. Sense a “but” or two coming? Read on.

It’s the performance version of Audi’s entry-level A3 sedan, nearly a foot shorter and $10,000 less than the compact S4.

Prices start at $43,850, including destination and the standard Quattro all-wheel drive. So far, so good.

That’s less than the BMW M420i xDrive coupe and Mercedes-Benz AMG CLA45 4Matic (which is called a coupe but has four doors), probably the two most comparable…