The biggest thing OnePlus has in its favour is fast and frequent software updates. I love OxygenOS. It's in the little useful things like screen-off gestures that impressed me initially with the OP3. It's how they've kept a 4 year old phone feeling fast and fresh so many years later. My daughter is still using it, and doesn't want to upgrade, even when I've offered. And it's not lost on me how it went from Android 6 all the way through 9 last year. They've got the software support figured out.
Beyond that, don't get caught up so much on what's on paper. Sure, that will give you indications about performance, but it's not the same as feel in the hand. For instance, my soon to be retired LG G7 "on paper" is far better than that two years older OnePlus 3 ... but I'd still take the old OnePlus over the danged LG any day! And a lot of that has to do with the software. Even if the G7's hardware is better on paper.
Figure out what matters most to you ... specs on paper, or experience in the hand. Which can be hard when you're not a tech YouTuber who gets all of the top flagships thrown at you to use and compare for free!! LOL