I use a Z10 as my daily driver. The android runtime has become better now after numerous OS updates .They are now faster than before .I have installed lot of android games as well as native games. The difference i find is in terms of battery life. Android apps somehow drains the battery much quicker. I have no idea about how it is in jolla , but from the reviews i read before deciding to go for Z10 , what i understood was , the runtime was now better in BB after lot of updates. Installing by just clicking the apkfile through filemanager is now possible in BB as well .And the free RAM of about 1.2 GB after booting also helps.
But i am not convinced about the extra layer of security that someone said. I haven't found anything like that.I could install anything and a lot of times i have ended up installing spam apps(Outside the appstore ofcourse). The apps that i have found to be not working are the ones which uses low level functinality .(Eg : droidVPN). It is a security feature for some and a weakness in the runtime for some.