I’ve used both iphones and Androids. Battery performance degrades past 2-2.5 years regardless of brand or OS.
If you replace the battery only, the iphone is still snappier because the android probably has a bunch of junk slowing it down. That’s the downside of having more freedom to install and store stuff in your phone. If you reset it, it works just fine. iOS gets around this by preventing users from doing anything. My jailbroken iphone had the same problem after 2 years.
There are some light users who would rather not have to deal with that, and prefer a locked-down OS. That’s fine. For me, having to jailbreak just to sideload apps is a dealbreaker, so I use Android.
Having only one dominant OS is bad for consumers anyway.