Yeah, we are well aware. The issue is that, under equalization, Dante is now using Nasuverse rules since his magic's rules are blatantly undefined. Which means he's using mana, and although he likely has an actual boatload of it, he can still run low.
From what I can tell, the issue is that Emiya can play defensively against Dante with little effort. After all, a similar, albeit smaller gap existed between him and Heracles in the Fate route of Fate/stay night, and while Emiya was weakened and unable to use either UBW or his higher level projections, he managed to kill Heracles
6 times. Without support from a master, without his trump card, and while injured.
I figured Dante's arsenal and larger AP difference would make this a much more even fight, but Emiya is extremely skilled at playing defense against far stronger foes. And by the time UBW is able to go up, he's either been fighting Dante from range for god knows how long, or fighting him CQC for a short while, both exhausting Dante, which we know is one of Dante's massive weaknesses.
By the time UBW goes up, Dante has been either pelted by high level ranged projectiles, or he's been fighting someone he just can't hit at CQC. Both would force him into DT, or even SDT, likely around the time Emiya pulls UBW. But then that means it's all over, because UBW can just do
this with everything Emiya has. I don't think Dante has a proper response to sword rain of that level. Vergil is one deal, but this is quite literally thousands of times better.
When I made this I was mildly convinced that Dante would win because of his amps and SDT, but I forgot how good Emiya was at playing defense. By the time Emiya stops playing defense, Dante doesn't have a true answer.
Between Emiya's adaptability, his defensive skill, and UBW's quality, I'd say this match reach a pretty safe conclusion.