Anecdotal, but my friend has been complaining for over a year that the updates are making his iPhone too slow. Otoh, my 6+ year old Android phone is still going strong (after 1 battery replacement).
Your friend's iPhone will go a lot faster after he also gets his battery replaced. Once the battery degrades too much the iPhone slows itself down in order to not crash by trying to use more power than the battery can provide.
