The one I use of course! The Royal Heavy Duty Commercial Upright... However honestly despite what you may think due to MARKETING, the top two most powerful upright vacuum cleaners are still the Royal and Kirby. But with that said the BEST answer truly is THE ONE YOU WILL USE! Both the Royal and Kirby seem to stay in the closet due to being so loud and heavy. So I recommend an ORECK! Only eight pounds and works outstandingly good! These three are the ONLY vacuum cleaners Ultra Clean recommends.