Startup: Flutter tends to be a little slower to start up, especially the first time, as both the Dart virtual machine and the Skia graphics engine need to load. This usually means a delay of a few tenths of a second. For larger applications, the difference can be up to 2-3 seconds slower on first load than a native application, but this can vary depending on the device hardware (e.g. processor speed, memory) as well as the application.
Native functions: Flutter also provides access to native functions, but this usually requires the use of various plugins, which are not always of satisfactory quality. For more complex applications, it may be necessary to write native code to improve performance.
UI performance: Although Flutter's performance is close to native, in some cases the animations, scrolling performance or implementation of device-specific features may not reach native levels. This is because, in a native environment, applications have direct access to the hardware, so rendering can be up to 10-20% faster, especially on older devices. However, this is usually only noticeable in Flutter for intensive animations.