Years ago the advice to mechanical engineers who were supposed to be designing machines was that the washer basket should be 15 liters per kilo of dry clothes if it was a toploading washer and 10 liters per kilo of dry clothes for a frontloading washer.
Then things started to change, and lots of frontloaders who claimed a higher efficiency and better cleaning started coming out with 45-liter drums for 5 kg of clothes, as seen everywhere. And toploaders with as little as 12 liters per kilo came out. That doesn't mean necessarily that the washers wash any worse than the old standby, but it can certainly mean they are not as gentle. Complaints about clothes not lasting as long have been heard for both kinds of machines.
There are good and bad reasons to pick either volume or weight as a yardstick to compare machines.
If you pick weight, then you are more likely to compare actual performance and you allow for machines that become more efficient at the task even if the drums are smaller.
If you pick volume, then you are more likely to see that manufacturers claiming to wash outrageous amounts of clothes in a smallish drum are lying.
Neither is a good guarantee that you will spot the lie. Notice that the "efficient" machines have only one liter less per kilo than the standard ones: 45 l / 5 kg = 9 instead of 10. And there are plenty of top-loading washers that *look* like the basket is huuuge and they certainly claim the full capacity, but when you read the instructions, they say something along the lines of "load up to the top line of holes in the basket" or "until the clothes reach the holes the softener comes out of in the agitator" which in any case is several inches lower than the top of the basket and makes them wash way less than competing machines with supposedly smaller capacities.
And even when the machines are supposedly identical -- years ago, Consumer Reports tested two "identical" machines from White-Westinghouse, one was sold under the Frigidaire label, the other under the Westinghouse label. One had a straight vaned agitator, the other one a spiral agitator, if memory serves me right. When tested for proper clothes rollover, one of them washed 14 pounds and the other something like 10 or 12. They were both labeled, of course, "extra-large capacity, mumble-mumble cubic feet".
The sad truth is that consumers should be informed of *both* how many kilos/pounds of clothes the machines can effectively *clean* and how much *usable* capacity they have -- it makes very little sense that a comforter that can stuff a washer to the gills may actually weigh half of the load the machine can clean when it's a full-load of cottons, for example. It's perfectly possible to have a washer that can actually *clean* and *rinse* a full load of 6kg/13lbs of cottons and can't deal with a 3kg queen-sized comforter.
For that matter, consumers should also be informed of how well a machine *rinses* and spins too. People are catching up on the spin issue, altho mostly we discuss how fast they spin, not how dry the clothes are at the end of the cycle. And I find that too many machines still rinse so poorly that many people who are told by their doctors/dermatologists about how they have to use detergents with no scents and/or enzymes or avoid fabric softeners at all costs are just sick because their washers can't rinse. I lost count of the number of people who claim to have skin problems I helped by just washing their stuff on hot water with top-of-the-line detergents, rinsed the clothes well and then put fabric softener (just enough, not fill the cap until it overflows) on the last rinse. Their skin cleared up pronto. They were just wearing poorly washed and poorly rinsed clothes, which made their skin flare up.
But we're not set up for measuring performance, that is actual *work* that only people who *like* washers and/or laundry will pay attention to. The "energy" labels just come from some poor person employed by a government agency that really doesn't care that much (even if the employee themselves did care) and all they want is a "standard". Which doesn't really tell us how well things perform, they just spit a number or a few numbers. Just look at the washers which get an EnergyStar label but wash with less than 60C/140F for a "hot" wash -- people with real allergies to stuff like dust mites will have a hell of a time with clothes washed in warmish water. Do you think the manufacturers care if the clothes are clean or rinsed if they can get the EnergyStar label? I have a bridge to sell you then. Also, to pile on top of that pile, I'm not sure if they fixed it yet, but the EnergyStar labels for dishwashers were given based on a test that ran the dishwashers with *clean* dishes (hey, at least they *loaded* the machines, it could be worse, they could have run them empty), so the machines get an EnergyStar label and then, when you run them at home, if they have a sensor to see if the dishes are dirty/clean, they use way more water and energy. Also, at least one manufacturer of dishwashers in US chose to "save" water (and thus energy) by providing only one rinse. It may work just fine for water that is hard or medium hardness, but for people like me that had soft water, it didn't rinse enough, so the dishes got etched. Users had to select the pots-n-pans cycle to get more rinses, so the energy efficiency was lower than other machines that had no EnergyStar labels. Yuck.
Until we have real tests that closely mimic real-life situations, and better standards, I would trust a friend's recommendation over any manufacturer's claims or energy labels. Don't take those capacity claims too seriously until you've seen the machines run, is what I say. YMMV.
