The washable tub is worth the cost from online suppliers. Or from local DME if insurance will cover.
As long as you have more than one tub, put any of the disassembled tubs in the dishwasher. At worst, you're out the cost of a tub.
I even wash the older style "unopenable" non-dishwash tub. They're not that hard to disassemble as long as you figure it out once and have a spare in case you break it. I'd rather risk some sort of damage to the tub than risk having crud growing in the tub because I couldn't clean it well.
I've washed my "unopenable" tub in the dishwasher dozens of times. The aluminum may be a little bit "frosty" looking, but I'd still rather have that than a tub I really can't wash well.
I really like having two tubs so I can wash one, and let it sit dry for a week to help prevent germ growth.
The S9 tanks have an advantage in terms of seals because even if the seal goes bad, it can't leak water into the machine because the water says entirely within the aluminum tub. There are no "wet" seals like in the PRS1 water tanks.