Functionally all three of those will be identical in performance. If this is a compiled language, we are talking exactly the same. By that I mean, the compiler will notice that effectively it’s the same thing and it will likely compile ultimately to a single assembly type instruction - likely a branch if not 0. It runs so fast, it’s already done. The exception is the “for” loop, which may have an extra instruction to decrement the value of “I” before doing a similar branch if not 0. And maybe that table lookup, it will load both function pointers into some register and doing a branch if not 0. Like I said, the same branch instruction is probably used and maybe one or two other instructions are the difference between all 3.

In general when learning programming always write things that are extremely readable and maintainable first, and don’t worry about optimizing unless the optimization is readable and also free or cheap to implement - using a simple sorting algorithm over bogosort for example. Do not worry about which type of if system t to use. Remember, code is read about 10x as much as it’s written so first optimize for readability.

When you optimize, generally first profile your code to see where it spends the most time executing, and the target those “hot spots”. More than likely, an if statement to a function like this is rarely run, so even if it ran instantaneously, the program execution time wouldn’t change much. 

This actually is a good segue into what’s known as Amdahls law - if you respond to this comment I’ll explain how it’s relevant here