There are several key differences. It looks like you can not restrict the transfers to your contacts, but you can specify "Preferred visibility" to see your favorites even when you are not using Fast Share. Sample recipients in the quick share screen suggest that this may be available on Chromebooks, iOS devices, and even on Wear OS smart watches, although we would not rely on everyone that is available every time the feature is published. The iOS version requires a special application.
It is not certain when Fast Share will start, although it is a feature of Google Play services and probably will not require Android Q. However, Google may not wait long. The company has warned that it is neglecting NFC-based Android Beam transfers to Q. As such, Fast Share may be the only way to quickly send files to local users without resorting to apps (like Google files) that your friends do not need are.