Moses wrote a deeper one, and Yeshua dictated one (recorded in four witnesses) deeper still. That's not to put down Sha'ul, but he himself would never consider his letters on par with the Torah or the Master's words.
Interesting that you should say so, because Peter does:
Bear in mind that our Lord's patience means salvation, just as our dear brother Paul also wrote you with the wisdom that God gave him. He writes the same way in all his letters, speaking in them of these matters. His letters contain some things that are hard to understand, which ignorant and unstable people distort, as they do the other Scriptures, to their own destruction.
~2 Peter 3:15-16