The same YouTuber has the Pixel slaughtering the Galaxy S7 Edge exynos variant too.
There are always variables than can affect app opening in this scenarios. Was the iPhone a 32gb model with reportedly slower storage memory ? Just for one example.
The main thing to take from any of these types of videos is not who wins, just our phones are very fast and capable. No one is really complaining about the speed an iPhone or S7 or HTC 10 opens an app.
Display, eco-system, battery, audio/headphones and to an extent camera (though again in the top smartphones the camera differences are mostly moot at this point, with more similarity than differences) and generally one of the greatest factors, PRICE ....
Anyone buying a 2016 flagship or even 2015 flagship is getting a very solid peforming phone all-round.
Yet internet being internet, forum posters being forum posters, and allegiances formed - people fixate and hate on all the small differences between the devices. Addicted to defining the 'best' and most often than not the 'best' just so happens to be the device they chose ... as if validation from random strangers on a forum and the belittlement of others choices somehow matters.
Sadly as of late, all the threads seem to all become akin to cesspits, demonstrating the very tit for tat nonsense behaviour to its finest, and beyond tiresome...
So everyone engaging in the constant nonsense and turning the alternatives section into a bitter twisted hole, please stop ....