My experience after owning iPhones since 3G and also same time owning Samsung from s3 to s9 and note 4 to note 8, and the max I stayed on Samsung was note 4 which lasted for 8 Months but sooner or later I will sell Samsung and keep iPhone for slowness and other annoying issue with Samsung .
This year I tried to give Oneplus 6t a chance and if I have to be honest, it’s prob the best phone I have ever used, iPhone X second close for me.
Oxygen os is much much better experience than Samsung one Ui, much faster, fluid experience, not a single lag, however camera sucks.
I am back to using my trusty iPhone X again but for me if manufacturers really want iOS users to convert to android ( if ecosystem is not important) then Samsung hardware and oxygen os would be a solid phone in my opinion.
Also my colleague has 3t which I got a chance to play with before buying 6t and 3t was almost same as fluid and responsive as 6t so they really shine at software.