Ok I break it down for you, I watched almost all the video reviews and written reviews alr. I'm also on iOS, iphone 7+.
The screen of the OnePlus 5 is 1080p pentile, which is bad. The camera which they hyped so much about is hit or miss experience, the bokeh effect is only good when it works. I can go on and on but you roughly know too much I don't go for it. Camera in the ip7+ is still stellar, can't possibly downgrade to a worse camera.
The phone's strength is that it is very fast due to the oxygen os, running SD835 and 6/8gb of ram. But don't be fooled, the phone won't be able to utilise all the ram, its mostly just marketing, just like it was on 3T as there is a limit to the # of backgrounding apps. They have scrolling jello effect when you're scrolling through apps, bad wifi connection. At this price range, I think not worth it.
I see YouTube reviews like all say very power, cos always been using IOS!! I know nothing about android

Any advise?!?