My first days now with the newest version of SailfishOS on the Sony XA2 are really impressive! In several stores with different quality levels there are masses of apps; the integration of android works really great, so even the android store is available and fast! (even if I not urgently need it). The system looks great and innovative, everything works also on a second view. So Jolla really does a very good job! Its the most developed system - besides the big two - as I see the things.
With no other OS I had so many problems with the installation. Without Windows it was not possible - and an USB problem made it neccessary to use also a second PC. One phone got bricked because Sailfish is (until now) not installable on devices flashed with Android 9. Jolla stopped carrying out the system for a while and tries to find with Sony a way to reanimate such phones.
If I compare the funcionality of the browser and other standard applications like navigation, mailing, messengers or just weather information, I miss a bit the pure functionality of ubuntu touch. And especially the way to switch from one app to another, the solution on ut is for me much more handy. And at the end I would prefer some selected apps instead of masses.
By the way: On Sailfish there is an app called 'Crest'. Here you can see how many processes are actually running on the phone. Compare if the android support is On and Off. You see maybe 2 processes if its Off. You see more than 20 processes if its On - even if you haven't opened any app ever in your live. Normally the android support automatically starts and can be started only through apps, if you have stopped it.