what is the best shader?

Another +1 for Sildurs in addition to Distant Horizons mod that allows LOD so 200 blocks away can be rendered in at a lower quality. Gives the game a massive scale.

I don't think there's a "best shader".
Each shader attempts to portray Minecraft in a different way.
I recommend downloading a bunch of shaders and switching between them from time to time.

I recommend Seus or BSL. They are very good shaders.

Always used Sildur, even the light one is good. Otherwise, I enjoyed Complementary as well.

Use the ZEUS Shader!!!!!!

I like Sildurs shaders. To me details are awesome