Firstly, age only negligibly matters in NV so don't bring that in as a factor. And yes, I agree that Obito was dumbed down is his fight against Minato for Minato to win because Kamui is way too hax to handle even for an epic technique like FTG solely because of the intangibility factor. And yes, a second face-off between Minato and Obito would go in Obito's favor because of the superiority of Kamui (the first face-off would also be Obito's if he wasn't dumbed down). But if we're talking about teleportation speed only, then FTG is faster because Kamui warping takes time. But Kamui is overall superior.