Based on previous experience with Samsung devices, absolutely do not buy any based on promises the company makes about the future. Buy it based on what is proven to work today(probably good advice in general, but plenty of people have been burned by Samsungs promises).
I'm not sold on Samsung's "behind the screen" anything. The fingerprint sensor in my wife's phone is embedded in the screen, and it just doesn't work. The sensor on the back of the phone was much, much better.
https://youtu.be/kMJEYDZT_JE?t=230