They are not used for the same things. The only common usage is as monitors.I'm curious... how do you balance your usages with the 2022 Tab S8 Ultra and 2021 iPad Pro? Is it a matter of which one that needs to be charged?
For this usage for instance I need to annotate the work of my university students and it's more effective to have them all at the same time, so I have multiple displays/tablets (iPads, Surface devices and Galaxy Tabs) on my desk (with stands that allow me to put one above the other and can compare and annotate them)
Otherwise I use the S8 ultra mainly for watching movies, while the M1 is used mainly for watching youtube.
The 2018 12.9 is used a lot to view PDFs/Word documents in portrait mode for work or for displaying sheet music on my piano. And they all have many secondary usages too.
But indeed I sometimes also choose to optimized battery health. I generally charge up to 90% and if sometimes I don't hear the shortcut warning me to unplug at 90% I use the iPad I accidentally charged to 100% before the others (none of this is necessary with Samsung tablets, which can stay plugged in all day since I use the option to limit the charge to 85%).