Issue #496
Read this Restoring Purchased Products to understand the purposes between the 2.
From iOS 7, every app downloaded from the store has a receipt (for downloading/buying the app) at appStoreReceiptURL. When users purchases something via In App Purchase, the content at appStoreReceiptURL is updated with purchases information. Most of the cases, you just need to refresh the receipt (at appStoreReceiptURL) so that you know which transactions users have made.
Users restore transactions to maintain access to content they’ve already purchased. For example, when they upgrade to a new phone, they don’t lose all of the items they purchased on the old phone. Include some mechanism in your app to let the user restore their purchases, such as a Restore Purchases button. Restoring purchases prompts for the user’s App Store credentials, which interrupts the flow of your app: because of this, don’t automatically restore purchases, especially not every time your app is launched.
In most cases, all your app needs to do is refresh its receipt and deliver the products in its receipt. The refreshed receipt contains a record of the user’s purchases in this app, on this device or any other device. However, some apps need to take an alternate approach for one of the following reasons:
If you use Apple-hosted content, restoring completed transactions gives your app the transaction objects it uses to download the content. If you need to support versions of iOS earlier than iOS 7, where the app receipt isn’t available, restore completed transactions instead.
Refreshing the receipt asks the App Store for the latest copy of the receipt. Refreshing a receipt does not create any new transactions.
Restoring completed transactions creates a new transaction for every completed transaction the user made, essentially replaying history for your transaction queue observer.
More about receipt, from WWDC 2017, What’s new in StoreKit session https://developer.apple.com/videos/play/wwdc2017/303/
You can also watch WWDC 2017, session Advanced StoreKit for more detail https://developer.apple.com/videos/play/wwdc2017/305/
Original answer https://stackoverflow.com/questions/45615106/when-to-refresh-a-receipt-vs-restore-purchases-in-ios/52162283#52162283