These numbers were measured using apkanalyzer,
which is also built into Android Studio.

On iOS, a release IPA of the same app has a download
size of 10.9 MB on an iPhone X, as reported by Apple’s
App Store Connect. The IPA is larger than the APK mainly
because Apple encrypts binaries within the IPA, making the
compression less efficient (see the
iOS App Store Specific Considerations
section of Apple’s QA1795).

Note:
  The release engine binary used to include LLVM IR (bitcode).
  However, Apple deprecated bitcode in Xcode 14 and removed support,
  so it has been removed from the Flutter 3.7 release.

Of course, we recommend that you measure your own app.
To do that, see Measuring your app’s size.

Capabilities

What kind of app performance can I expect?