Solid Tubs
I only have solid tub experience with SQ 1974 or 73 model, other here will have far more info: My main fun with them is they are SO DIFFERENT than all the perf tubs, it's plain good fun for a real washer hobbyist to see the differences.
1) Time fill instead of pressure switch----some guesswork and water line pressure is involved, there's a learning curve.
2)Overflow rinsing--SQ and many others---overflow near the end of the wash cycle, lifting suds and dirt up and out of the tub while it agitates. Also it dilutes the wash water and you're half-rinsed before it spins out the first time.
3) Spin-out------no holes for slow draining, no 3 minutes to drain a tub. The soild tub spins out into the outer tub in maybe 20 seconds, then it's just up to the pump to catch up, but the clothes are already damp dry. My GE and Maytag and 1-18 all have tons of water for one to three minutes, straining thru the washed clothes, leaving some dirt behind.
4)Agitated rinse overflow cycle----SQ and maybe more--agitation starts for rinse when the water level is maybe 85%, then continues while more water helps overflow the tub. Rinsing is FANTASTIC. Then with no excess water it continues to agitate for 2 minutes, then again more overflow water enters the tub for more lint/dirt/floaters to rinse over the side while agitating.
5)Some or all that excess water is made up for by the fact there's no outer tub to fill. Think of how much space GE and Norge have in the outer tub, excess water beyond what's necessary for cleaning/agitation/turnover. In a solid tub, all the water is for clothes, not to fill empty space between the wash basket and outer tub.
6)Great rinsing
7) Most important for me, it's simply a different machine, different operations, diffferent behavior than perforated tubs. Good clean fun for a hobbyist, just like a hobbyist also needs to experience a Hoover Twinnie and an Easy Spindrier a few times. And a good old Maytag wringer or Speed Queen wringer. Fun change of pace.
Of the major US brands, Neither Maytag nor WP/Kenmore ever made a solid tub. GE switched from solid to perf some time in the mid 60's, Frigidaire in 70 or 71, so Speed Queen, with solid tubs thru maybe 76 or 77??? was the last major manufacturer to stick with what had been a 40's-50's technology. Which at times makes it easier to find this exact make of solid tub than others.
As I said, my solid tub experience is limited to SQ 73 model. Some other makes did overflow without agitation, some did pressure fill with the first cup or so of overflow water kicking off the valves. Some do suds saving, etc. Hopefully other will chime in with other bransd of solid tubs.