There is significant weight savings. I picked up the steel wheels and tires an then the aluminum ones I just got wow what a difference! I haven't weighed them yet but it seems like 1/2 the weight.
2004 Chevrolet Silverado 3500 LT with a 2004 Jayco JayFlight 29BHS
2014 Greyhawk 31FS with a 2007 Tahoe toad
2014 Thor Palazzo 33.3 with a 2007 Tahoe toad