Then XR is the midgrade of briggs engine that carries a 2 year consumer 1 year commercial engine whereas the Vanguard is the true commercial engine with a 3 year commercial warranty.
Briggs basically makes 3 grades of horizontal engines The CR or consumer rated the XR extended rated and the Vanguard. From Briggs own literature the XR has a life expectancy of 3 times the CR where as the Vanguard is rated at 8 times the life of the CR.