C#: params keyword vs. list

The params keyword is syntactic sugar handled by the C# compiler. underneath the hood, it’s actually turning

void Foo(params object[] a) { ... }
Foo(1,2,"THREE");

into

void Foo(object[] a) { ... }
Foo(new object[] { 1, 2, "THREE" })

From a performance perspective like you’re asking about, the params call is simply faster because it is a bit faster to create an array than it is to create a List<>. There is no performance difference between the two snippets above.