Yet another Unity3d user here. Don't think the file size is too big a deal for Android, just shipped a game with a lot of textures for procedural characters & UI and a few sounds and the APK still came in around 30MB. All depends what you include in the game really.
Big selling point for it is how easy it makes cross platform dev, we worked with iOS as target platform for most of development (we had more of the target hardware to work with) but when it came to switching to Android it was incredibly smooth.