The only difference you will see is when your function yields back to others and when it performs its operation. You can also have a wait in the middle if that tickles your fancy, your local variables and my and you will be restored. However, note that wait() allows other functions to resume execution which may or may not have side effects on globals that you have to take into account. Of course only if it applies to your use case.

Something I really want to stress though: You don't need a wait() in your loops if they terminate by themselves! That is, unless you have a loop that you want to execute once per frame (or in similar intervals), putting a wait() will be decremental to your performance! I see that way too often that beginners assume that a wait() is a must within a loop or otherwise their program will halt.