Just take a Northstar V-8 Hemi hooked onto a Hoover and you can veritably suck the very magma core from the earth! At least that's what a namesake of mine said one time.
The truth be told, they all suck to different degrees. Having only bought a stainless steel wet dry vac for the work that I do, all the others are second hand that always were tossed for the following reasons: 1. Hair tangled up in the beater bar or belt broke. A lot of customers just don't have the gift of gadget and give up on doing anything other than emptying the bag. 2. Clogged hose on canister units or tube in top filling upright vacs. Even the standard Eureka will get clogged up at the base where the bag hooks up. 3. Blades sheared off from detritus being sucked up like marbles, rocks, plaster and things better off in a shop vac. 4. Wrong setting on the vacuum for the surface.
Much of this can be avoided with proper instruction from a sales rep or somebody like me who messes with everything. But when consumers see this on a shelf at the Costco, Sam's Club or Sears they only see the PR that's written on a pop display and figure that's all there is to it.
Lesson I Find out how to get the beater bar assembly apart and change the belt. It's in the manual or on the box usually. But if there's ladies, dogs, and big hair metal heads from the 80's around, there is going to be shedding. (I'm not talking asbout the Hair Club dropouts and Bichon owners that don't have girlfriends.) If hair isn't tangled up in the beater bar the belt will move it better.
Lesson II Listen to the pitch of the motor as you run it. It the business end is stuck to the floor, there is no air movement and the pitch of the motor is high. Raise the level up untill the brushes just make contact without making a seal to the floor. If there is a clog inside the vacuum the motor will wind out too and it's time to get the hanger out while you take it apart for cleaning. Some time a broom and shovel should be used on the floor first cause these things weren't intended to suck up wood chips, shell husks from the aviary, small toys from the playroom or scrap pot metal from the garage floor. Mount a 2 x 4 on a broomstick and use a dustpan first before wasting time, tools and temper on Royal Kirby.
Lesson III Most machines are fixable. Though most modern vacuums have brass bushings instead of ball bearings. they are pretty tough and resilient. If the shaft of the motor doesn't wiggle much and turns some, it's likely the blades have sheared off due to the unit sucking on something it shouldn't. The Blades cost less than $5.00 (3.5 GBH). Belts are on displays at the supermarket. As are the bags. Believe it or not, these things work real good when they're not full. Clean and dry sponge filters once in a while if your unit has them. Unless you can buy new cars when the ashtrays are filled up or you have paper for body parts, let use the nut between our shoulders here.
Lesson IV Match the tool for the job. If you're going across bare floor the brush is just going to knock stuff around. An electric broom does fine. If you have shag or sculpted pile carpets you need something to beat and comb the snot without an aerobic workout. Most vacuums have tools available for purchase if they don't come with them. The better models will hook up to or power sanders, drills and all sorts of things.
All said, they all do okay for what they are intended. Uprights are rated in Amps and canisters are rated in HP. But given a little thought to how you are going to use it and knowing how to maintain it, a vacuum will last for twenty years or more.