Multi-Platform Subscription System or In-App purchases - whats better?

While for the end-user an In-App purchase might look more practical at a first glance, it has several disadvantages for both the end-user and the app owner over a Multi-Platform Subscription System:

1. It would no longer be a Multi-Platform Subscription with single-sign-on for users. Instead subscribers would have to pay multiple times and create and pay for multiple subscriptions - one in each app separately. Every time they would like to access their subscription on a new device, with an app from a different app-store, they would have to pay all over again for an additional subscription.

2. Some app-stores are very restrictive when it comes to in-app purchases, and it is very hard to get In-App purchases approved. For example if purchases are made in a different currency than USD + the combination of both regional (Geo Location Restricted) content, and content available to all users worldwide, would make it most likely impossible to get in-app purchases approved by the App-Stores.

3. Most platforms would take an additional cut of 20-40% out of your revenue. 

4. It would create an incredible dependency on the App Stores: they could take your apps down, or revoke In-App purchases at any time, at which time you would be losing all your subscribers. Or, they could suddenly increase their “share” of your revenue at their discretion. You would have to accept any and all terms they impose on you, or you would lose all your subscribers. 

5. All your subscribers would have to register and pay for your subscription multiple times if they want to have access to your content on other Apps, such as FireTV, Roku, AppleTV, AndroidTV, iOS and Android mobile, your website etc.