What "cross-platform" actually means today
Flutter compiles to native ARM code and renders its own UI, rather than wrapping a website in an app shell (as older hybrid frameworks did). That means a well-built Flutter app can look and feel native, run at native-like performance for the vast majority of app types, and ship to both the App Store and Play Store from one codebase.
When Flutter is the better choice
For most business apps, MVPs, internal tools and IoT companion apps, Flutter is the faster and more cost-effective choice — one codebase means one set of bugs to fix and one team to coordinate, and features ship to both platforms at the same time instead of twice.
When native still wins
Apps that lean heavily on platform-specific APIs (advanced ARKit/ARCore features, deep OS-level integrations, or apps where every millisecond of animation performance matters, like some games) are usually better served by native Swift or Kotlin, sometimes with Flutter used for the surrounding app and native modules for the specialized parts.
A practical middle ground
It's not always all-or-nothing. Flutter supports native platform channels, so a primarily cross-platform app can still drop into native code for the one or two features that genuinely need it — which is usually a better outcome than committing to two fully separate native codebases up front.