Suds
I have 2 Kenmore belt-drive era suds models, and a GE Filter-Flo suds model. I use them all the time, but I'll admit that having all of them hooked up in a line-up of 4 total washers allows me to immediately re-use very hot suds instead of a single machine setup where i'd have to let the water cool 20 minutes or so during deep rinse and final spin before sucking the suds back into the one and only machine.
If I change the oil in the car and get messy, or I clean up after a dog or an infant, I don't re-use the water. But for my business office clothes, sheets, towels, etc, I separate out 2 or 3 loads before starting. My usual doings are Hot water in the 74 Kenmore for towels, sheets, socks and boxers. NExt that water gets sucked into a 1960 Whirlpool for pants. Final is a 1979 Filter Flo for shirts. By then it's lukewarm water, perfect for perma-press. And the GE has all that rivers of water for the spray rinse, so believe me I wear clean clothes with no ick factor. I watch the deep rinse in the GE, it's always pretty clear water.
Everyone is entitled to their habits and preferences, and I would enjoy suds less if I had that 20 minute wait between loads, but as a laundry hobbyist with 4 installed machines, it's great.