Hard to tell from the code but it looks like SwitchOnInt acts a lot like a switch statement in C++, so it’s not too bad. But still, it’s going through every value and comparing them one at a time so it’s not ideal.
For something super-fast you’d want to just index an array. Then there would be no performance hit for adding more pins. But it seems that would require some custom coding in C++ to fashion your own node and it doesn’t look like it would be especially easy. You need to interface with the editor and the compiler.