I agree there's a tradeoff. And that in the scenario where Apple allows alternate app stores, there would also be tradeoffs. But I disagree with your view that it would have to resemble the situation on Android. I feel that the Apple brand and the inherent security features of the iOS environment- which aren't simply the exclusivity of the App Store and the App Store Review process- could lead to secondary stores that are carefully curated and have a higher bar of security than the ones you see on Android. In fact, one could very well imagine companies entering into a new market and providing secure app markets that try to beat Apple at their own game (such as searchability). For one thing, there's more money to be made with iOS apps, and perhaps that could lead to greater investment and higher quality stores.

I view the dismissals of "secondary app markets will just be like insecure shoddy secondary Android app stores" to be both pessimistic and lacking in imagination at the potential for new businesses and innovation to be created if Apple just gives up a little bit of its dominating power.