NYC Writer, I would disagree
I strongly disagree with your statement of " simply not as much weight pushing down on the beater brushes." Uprights are heavier than canisters, but the weight on them is positioned so it pushes the the the rear of the motor base actually pulling the front of the hood further off the floor. If we were in a situation of no wheels and no springs on the bases your analogy would be more correct, but you'd still notice the front of the head lifting off the floor quite a bit.
Now when you put wheels and springs into place on various machines and you figure in length of bristle then it changes everything. All of these machines are so controlled that weight doesn't do much anymore. If the height setting is wrong or machine is just poorly designed then the head acually doesn't hug the carpet too well. As example you had thought about Sebo. Many of those machines use a computer chip to electronically adjust the height of the machine. Many of us have found this feature to be flawed as we feel it never adjusts properly and does not go down low enough. The Hoover Decade line uprights from years ago were great on a variety of carpets. But if you had a very low profile indoor/outdoor rug some of those didn't get low enough to seal well with the carpet and do a good job.
Now on a canister vacuum many of those power heads do not have a manual height adjustment and they are positioned that when on the rug, they automatically adjust. The vacuum suctions is further able to pull the lighterweight cleaning head further into the carpet pile and really give a deep clean. Some examples of nozzles that do a great job at this would be the Eureka Express, Hoover Windtunnel and Electrolux heads.
CenTec is a manufacturer that designs canister vacuum power nozzles for many different central and canister vacuums on the market to include all current Panasonic and Kenmores. While good cleaners and powerful they are not perfect. If you took one of these power heads and put it on flat table, you would see that the height adjuster systems actually has the unit skewed. It does not sit level and is higher on one side than the other. The brushes on these are also short cut, Bissell agtitators tend to also be short cut. So again these actually clean good, but for those of us that want a deeper clean, like myself I would not be using one of these machines for the thorough deep down vacuuming of my rugs!! Hence I have NOT recommended any Panasonics or Kenmores to you!!
Now if you do the above test with a Hoover Windtunnel head, it actually looks like there is a slight gap in the front which allows for airflow to get in and airflow is what moves the dirt into the suction stream towards the bag. The nozzle is completely level with the surface of the table and units agitator brushes are bent down into the surface of the table. Most Hoover agitators have slightly longer bristles helping the cleaner really dig deep down into the pile. Hoover cleaners are still some of the best on the marker for deep cleaning due to their design. Hoover's problem is that they have skimped on some quality aspects lately and shifting most production to China. I do recommend Hoover to you for their cleaning but since your budget is unlimited we've posted higher end vacs with greater durability while still cleaning well.
One reason that canisters do so well is because of their central mounted air duct. Most vacuums on the market today are called "Clean Air Design" This means that the dirt goes to the bag before going through fan. The task is accomplished by dirt being sucked out of housing by a separate hose that attaches to ONE SIDE of the nozzle. This is the problem. Upright vacuums are plagued by this factor of the airway only set to one side, so cleaning effectiveness is not even across the base, and the far end doesn't get cleaned well. In a canister the air path is in the center so the suction is even across the entire agtitator cavity base. Many canister vacuum suction motors are larger than on an upright so they're capable of more CFM's and overall power, thereby despite the suction motor being further from away, the higher power compromises and allows them to perform extremely well in deep cleaning carpet. This same principle is why a household central vacuum system that uses an electric power nozzle is one of the absolute best ways to thoroughly deep clean a carpet!!
Again I'll say that I'd put some power head canisters up against the best uprights. It doesn't matter which vacuum you use in a test, the vacuum cleaner that use last after a series of other vacs will still find some dirt, assuming it is good a unit.
Now since you have been hesitant towards a terrific canister option I have heavily recommended the Riccar/ Simplicity Tandem Air uprights for you as well in posts, and here is a youtube video of why!!!!
) If I'd been using something with a finger tip switch, it never would have happened!
