Actually what is the differents on C# and JavaScript 
It’s not javascript but ‘UnityScript’ which is derived from javascript maybe.
The difference is that C# is widely used programming language and UnityScript is system proprietary.
But what is the best to use??
Whatever makes your life easier in the end. You can do anything in either language, but the syntax is different and there might be some workarounds. A lot of people on here use JS, but a lot use C#. You can easily get documentation for either language via Unity docs.
Whatever you prefer. There are already many topics on this subject, you can read them if you like. I’m sorry but we really don’t need yet another one.
–Eric