Hi, I can not report any performance details, but I don't know any extremely important reason for upgrading to 11 - instead, I found a good reason why to stick with Android 10/ LOS 17.1 for my milletlte:
I recently upgraded my "small" old Samsung Galaxy S4 mini GT-I9195 to LOS 18.0, and: several memory-intensive apps are not able any more to be configured to use external SD memory - which is most important for our old low-memory devices.
This is NOT a bug, this is Google purpose for ALL Android 11 and later versions. They prohibit the use of the external Card's "android/data/ . . ." folder. They claim that this is something like a dangerous "sharing" access of app storage data between all app that claim access to those sub-folders. You may quickly google the background (androidexplained, Android 11 Scoped Storage - Saving Files To Shared Storage).
Google Maps itself _is_ still able to be configured to use internal or external SD mode for offline cards.
HERE Maps (potentially using VERY large map files on tablets!!!) can not be configured like this, and the web rumours that there are a lot of other apps too...
I also tried HERE Maps Beta, which claims to be a total remake, but no success.
Even when the SD is configured as "internal" you can only select the internal memory. No matter if internal or external mode: for Android 11 devices the SD card mostly is ONLY useable for music, fotos, videos, data files downloaded.
If you don't believe me or you think you know better: please try it (having a good backup... ) and report here, please!
Good luck, or: good Android 10...