The first luchos were on a higher level than the second luchos, because they were fashioned by Hashem. But, of course, we all know that there is something better about the second luchos - namely, that they were not broken.
Now, in fact, since the first luchos were going to be broken, they don’t have a certain phrase which the second luchos do, because that phrase has a word that is not fitting for the first luchos. What is that phrase?