Describe what the app actually does
An application that is mostly forms, lists, and network calls shares almost all its logic across platforms. One built around the camera, background location, complex gestures, or sustained graphics does not.
Write down the features that touch the platform deeply. If that list is short, cross-platform is likely correct; if it is the core of the product, it is likely not.
Be honest about the team
Two native codebases require people who know both platforms, or two teams. That is a permanent staffing commitment, and it doubles the cost of every feature that is not platform-specific.
A single shared codebase maintained by a smaller team frequently ships more, even when each individual screen is marginally less polished.
Know what cross-platform costs
Access to a new platform capability may lag its release. Some integrations require writing native code anyway, which means maintaining a bridge as well as the shared code.
Debugging crosses an extra layer, and performance work is harder because the boundary is not fully in your control.
Know what native costs
Every feature is specified once and built twice, and the two implementations drift. Bugs get fixed on one platform and not the other, and behaviour diverges in ways users notice when they switch devices.
Coordination overhead is real and continuous, not a one-off.
Consider the hybrid arrangement
Shared business logic with native interfaces on each platform is a legitimate middle path — it avoids duplicating rules while keeping the experience genuinely native.
It is more architectural work up front and it suits products where the interface differs meaningfully between platforms but the logic does not.
Prototype the risky part first
Whatever the hardest platform-specific requirement is, build it before committing. A week spent proving that the demanding feature works in your chosen approach is far cheaper than discovering the limit at month six.
This decision is expensive to reverse, which makes early evidence unusually valuable.