I don't think we've seen the best of both yet.
In terms of potential, both are going to be part of the very strongest mainly because of their respective stats, lineage and Adcoc usage.
I said it when Yamato was introduced that she is very similar in stats with Zoro and the only difference between them will be Zoro's higher AP. Seems that is being proved right from recent chapters.
So just like Oden was on the same level as Roger, WB and Rayleigh, I think Yamato will also be on the same level as Luffy and Zoro even at EOS. The margins will be minimal at best.