Better power curves & higher RPM capability, so you can use a smaller, more underpowered engine for the same application. But that never overcame their mediocr

Better power curves & higher RPM capability, so you can use a smaller, more underpowered engine for the same application. But that never overcame their mediocre gas mileage (lack of compression/poor combustion chamber shape), oil burning (oil-lubricated apex seals), and need for frequent rebuilds.