Well, Cort is faster that Laporte on flat road, but he is terrible at positioning for bunch sprints, he always gets boxed out of position and loses wheels..... I simply don't think he is crazy enough, for those last 3K run ins for the big sprints.
So by "better" you mean positioning, you are right, but not on pure speed.
I'm not sure, Cort is necessarily faster on flat roads these days, but he most likely has the best potential of the two, if he did more specific training and improved his positioning skills/gained enough confidence to engage in the battles in the bunch. But if he did that, he wouldn't have the same climbing level, and then it wouldn't be a given, that he would win a lot more than he currently does. He should get a bucketload of podiums and additional top 5s and 10s though, and a Milano-Sanremo win would defiinitely also be easier to achieve.
He did beat Laporte in Paris-Nice, but that had more to do with him reading the finally perfectly rather than just being the fastest.