There are externalities to each choice, of course, but the correct answer is, actually, the obvious one. Apple is not in the right on this one, from any perspective. If they care about their users and developers: they'd drop the commission. If they cared about their revenue and investors: they'd drop the commission.
Fortnite's protest should have been the wake-up call for the people dead asleep at the wheel of their App Store division. Epic very likely would have stayed on the App Store indefinitely at 15%; the issue has metastasized, and now Tim Sweeny has taken the stance of "alternate payment frameworks or nothing", but I'd bet every dollar I've got that if Fortnite's IAPs were at 15% before they left, they'd still be on the App Store. Everything is about money at the end of the day; Apple doubled-down, so now Epic had to double-down.
Imagine a commission so reasonable that Netflix could sell its subscriptions there; that Amazon could sell books; that Fortnite could (maybe) return, and the next triple-A gaming hit that hadn't even considered mobile because of the commissions. That's the money Apple is leaving on the table. These companies WANT their products to be easy to buy; nothing makes that easier than App Store IAPs. There's a number that could work for everyone, but Apple comes to every negotiating table with their fingers plugged in their ears yelling "nah nah nah I can't hear you 30%"
Apple's App Store policies throughout the 2010s will go down in history as the biggest blunder big tech has ever made. I am absolutely certain of this. They're throwing away an empire that could last a hundred years, because they think they're invincible. Tim Cook literally said, under oath, "we don't know how profitable the App Store is". They've publicized proudly about how they employ five hundred whole people to do hundreds of thousands of App Reviews. This is not malice or greed; its complete and total incompetence. Why are investors not OUTRAGED at Apple's leadership?!