Reading Daved Beniam's comparison, I ask myself if he has the same New Outlook than most of us. With me, MS Support abandoned their attempts after three weeks and several solutions with the conclusion, that it was not possible to synchronize my Android OneCalendar App with New Outlook. Highly remarkable, since MS Mail and Outlook. com always synced with OneCalendar without any problems.
The other problem (unsolicited ads in New Outlook) would only be solvable by getting a paid Office 365 subscription, something I of course don't want either, since I already have a paid ongoing subscription to Office 2021.
I guess, we all have to wait, until New Outlook matures and offers the features MS promises it will offer.
Finally, a word regarding linking IMAP accounts. For me, it works with two IMAP accounts without any problems. However and again enter all data by hand, because copy - paste led to error messages several times with me.