Differences between using realloc vs. free -> malloc functions

Question

Why would one use realloc() function to resize an dynamically allocated array rather than using free() function before calling the malloc() function again (i.e. pros and con

Answer 1

I had a program that was doing a bunch of free() and malloc() calls to make a dynamic array, and I thought I'd optimize by reusing the existing array when possible. Benchmarks showed that realloc() on average is slower than just calling free() and malloc(). I guess it makes sense, since sometimes it would grow, and maybe require copy.