Personally I'm sticking with iOS until I have a clear picture what Sailfish and such are doing.

It's about trust really. Apple has made trust and security a major part of their platform. I'm on a phone that I bought 2nd hand and it has been getting updates for 5 years now. And they now have at least some history of resisting attempts to backdoor and modify their OS in stupid ways.

Android is different for every vender, but as far as I can tell the best you can expect, from launch, is maybe 2 years of updates that lag behind. You can also expect bloatware, and you'll always wonder exactly what google is doing to spy on you. Linux or not, won't trust it.

LineageOS I expect to be exactly what you'd expect a fork of android to be. Lets remove all the things! We'll get to making it better than android later, when we have time. I might be wrong about them.

SailfishOS is... I don't understand it. I don't know if it has literally any advantages at all over the competition.

Shame Ubuntu Touch is officially dead. I'd absolutely love to run it on my phone - they never sold me one though!