iPhone XR - better battery, better performance, guaranteed at least four more years of support, more secure, FaceID, beautifully written and well supported apps, no effort to maintain, no need for antivirus on your phone... I could go on ;-)
Only criticism is if you have an existing iPhone it might seem a little less exciting but when you have things going on in life this form of reliable and rock solid technology wins hands down.
The OnePlus I'm sure is great relative to Android phones, but don't confuse that with the iPhone! Android phones (and some nice Windows laptops) look great online and in marketing, and the spec-sheet, for sure, but if Apple does or ever did appeal to you and please you, it'll be hard to get that taste out of your mouth for anything that is even slightly different (read: more work). That's my experience.
I speak as someone who bought an iPhone XR in January 2019, sold it in May for a brand new S10+ and sold it 7 days later for.... another iPhone XR! Lol