Hello, it depends on your needs and budget. If you need a bigger screen and more powerful performance, you can choose the S8. If you need a smaller screen and a more affordable price, you can choose the SE.
If you need a better camera and a more powerful processor, you can choose the S7.
Personally, I think s7 is the best
The S7 has better performance and more features, such as a larger screen, faster processor, and more fitness tracking options. However, SE is more economical