Well.... I'd say 95% of my straight razors are vintage, this should give you an idea about my preferences. However, that is, essentially, what it all boils down to: preferences.
It could be argued that these days razor makers have a much deeper knowledge and understanding of the steel itself; all that goes into forging a blade, grinding it, all the technical aspects of the whole process, including modern machinery, all that is vastly superior than in days gone by.
Still, one cannot ignore the obvious know-how of the blacksmiths two centuries ago, same as no one can dispute Antonio Stradivari, G. B. Guadagnini or J. B. Vuillaume's tecnical prowess in violin making. Plus, in both cases (razors and violins), the results speak for themselves. Hou can't fault the quality, you just can't.
Modern razors give you the chance to customize them, however, if the maker is willing to engage in such exercises. That is a big plus because, if you're willing to put your money where your imagination is (it can get pricey), the possibilities are endless. I have just two modern razors, both made by Drew Dick. One of them was his creation, but the other one, well that was his first (and, as far as I know, last, so far) traditional kamisori. It was something I commissioned specifically. I also had the chance to offer my input in certain aspects of the design, both of the blade and the guard, and that makes it a truly unique piece.
But you are right in one thing though: ultimately, an edge is an edge is an edge. If the steel is good if the grind is good, if it is well balanced, if it feels good in your hand and is well honed, it won't matter if it is modern or vintage.