log-diff | log detail compare!

Firstly, a macro is just a form of textual substitution performed on the source code. Anything you write as a macro, you can also write as regular code. Check any C++ FAQ, it will tell you that macros are evil and that they are to be avoided generally. Your case isn't special, it doesn't benefit from use of macros.

Then, there are some points in your code that stick out:

• You're passing vectors by value to functions.
• You're returning vectors by value from functions.
• Using int for the size when modern auto is available.

This suggests you have some basics to learn still and/or that you're writing in the style of a different language. The latter then leads to non-idiomatic code which in turn might make it hard for the compiler to optimize.

Lastly, your second approach creates an alias to one of four functions, which probably boils down to a function pointer. This won't be inlined then. The redundant parameter to some of these functions is another obstacle for the optimizer.

Suggestion: Create four separate functions that take a vector and rewrite the current diff() to just dispatch to these according to your existing logic. Also, you do have measurements, but try to run this in a profiler. It will tell you more accurately where the time is spent, which may well be surprising.