Final answer:
A VR engine is characterized by its staggered V-cylinder arrangement allowing for a compact design, whereas an in-line engine has cylinders aligned in a single row, which is simpler but longer.
Step-by-step explanation:
What distinguishes a VR engine from an in-line engine is primarily the configuration of the cylinders. In a VR engine, the cylinders are arranged in a staggered V configuration that allows for a more compact design compared to a traditional V engine. This compactness is achieved by the overlapping of the cylinder banks, which entails a shorter engine block and generally a smaller engine width than in V or flat engines.
In contrast, an in-line engine has all of its cylinders aligned in a single row, typically standing vertically or slanted. This configuration usually results in a simpler design and is easier to manufacture, but it requires more space in the length of the vehicle compared to VR or V configurations. In-line engines are often found in smaller cars where the width is limited, while VR engines are typically used in vehicles that need to save space across the width of the engine bay, like sports and luxury cars.