get_permalink() is the original function, and is used to get the permalink URL for a post.
get_the_permalink() was introduced in 3.9 simply so the permalink function was consistent with the other post-related template tags, such as
get_the_content(), which are all prefixed with
The equivalent functions for echoing the result of those functions are the same but without the
get_, such as
the_title(), but in the equivalent for
get_permalink() is not
the_permalink(), so the lack of
get_the_permalink() was an inconsistency.
Using the function just calls
get_permalink(), which still exists for backwards compatibility reasons, so the result will be exactly the same.