The most relevant choice for add-to-app scenarios is for you
to decide when to pre-load a FlutterEngine
(that is, to load the Flutter library, start the Dart VM,
and run entrypoint in an isolate), and what the memory and latency
cost is of that pre-warm. You also need to know how the pre-warm
affects the memory and latency cost of rendering a first Flutter
frame when the UI component is subsequently attached
to that FlutterEngine.

As of Flutter v1.10.3, and testing on a low-end 2015 class device
in release-AOT mode, pre-warming the FlutterEngine costs:

42 MB and 1530 ms to prewarm on Android.
330 ms of it is a blocking call on the main thread.

22 MB and 860 ms to prewarm on iOS.
260 ms of it is a blocking call on the main thread.