I am waiting for one plugin to be ported to 2020 and then planning to switch. 2020 should be better than 2019, the command panel has a fix that makes subobject switching faster... maybe as fast as 2016 was :D
But the story of 3dsmax is a sad one:
2016 - stable, UI fast enough, viewports good enough - the 'gold standard' even after all these years
2017 - viewports much faster, buggy slower UI, and a critical bug with snapping that can crash Max at any time after using snap even once in a session, never fixed in 2017
2018 - stable enough, still a buggy and slower UI, and we came across a super annoying bug with instanced objects, mirroring and modifiers forcing you to work around by avoiding instances (fixed in 2019, it seems)
2019 - OSL, stable enough, this time the UI however got a lot slower than 2018, command panel and material editor UI refresh time is awfully slow
2020 - let's see...
As suggested above, if anyone finds bugs in 2020, please share. I'd hate to discover bugs mid-production as it happened now after we switched 2018.
I am pretty sure Max QA has no production experience whatsoever and runs simple usability tests only. It just can't be that they missed the UI bugs and slowness, modeling crashes and workflow regressions in the last 4 releases.