if you're trying to find out what's better, urethane would be my choice, if you want the best, nano,but it must be applied in dust free environment,since you have very small window to sand and polish out any dirt specs,even then it's usually very hard to polish,but if it's for a show trailer queen,urethane will be just fine, nano clear is designed is scratch/chip resistant,solvent,grease repellent as well as wax repellent,