Writing Unity plugins (for use in iOS/Android) -- worth the effort?

In my game I'm doing a lot of procedural mesh updating. This often involves updating multiple meshes vertex/uv lists per frame.

My code is clean and I get reasonable speed on iOS/Android...but having to budget 5-10ms for the operation on those frames doesn't leave much room for other calculations.

When dealing specifically with Mesh updating, would there be any benefit to writing a c# or c++ plugin to do the processing? The plugin would need to take a list of verts/uvs and spit out a Mesh.

I realize this is a sort of 'how long is a piece of string' question, since each situation will be different, but does anyone have any experience specifically with a native plugin doing mesh updates and was there a reasonable speed increase?

Thanks!