Also depends on how long you intend to keep the tablet. I have a 2017 10.5" Pro and I remember people saying the same thing about what is now a measly 4gb of ram, but it's kept this thing going now 5 years later, with no real need to replace it (yet) for at least another 2 (for my needs)
5 and a half year for my 2015 pro... at that time 4GB was massive for iPad... now it's normal, but still good... but others things don't age as well...
16GB is very future proof but problem with future proofing is that at some point other things become weak points
(in the old ipads lightning port, pencil 1, to some extent CPU, lack of compatibility with new accessories etc.).
Even the M1 could be improved with centered webcam, maybe better face ID, better screen coming to the 11 pro, bigger screen for those that would like that... Or even Apple moving to new sizes like 12in and 14in for the pro at some point, and all accessories going with that....
So it's very hard to completely future proof for many years (like 10 years for instance), let alone, after a couple of years, the loss of warranty, apple care and battery degradation (which can be replaced for a charge for up to 5 years after sales of new devices end).
