Lol this has been going on quite a long time. I still say Nero>New Vergil with mid difficulty. Their swordsman ships are different but neither would just outright dominate. Nero has dispatched enemies much stronger and faster than New Vergil so he can manage without having the ability to warp around like his foe. Hell New Dante downright destroyed New Vergil and I personally think Nero would beat New Dante too (but I'll save that for another time). Nero doesn't just have brute strength though he just uses it as his key for ending battles quickly. but seeing him keep up with Dante and his crazy stamina, bullet time with ease, dodge lightning from foes and that sealed room that Agnus locked him in for a while I'd say he'd put New Vergil down in only a couple hits once he tags him because he isn't put the pressure on him in an category but maybe intelligence (but that didn't help him in any of his other straight up fights lol)
The New Vergil while swift, kind of lack feats of any real kind. It's easy to say he's swift and fast but compared to who exactly? He's got a rep of losing so far. And while his attacks may very well be more swift than Nero's, he's not nearly quick enough to get around Nero's defenses to land a viable hit. It also doesn't help that I don't think he could put Nero down for good even with a clean hit. The kid has some pretty good endurance and resilience and a healing factor that helped him continue fighting when he was stabbed multiple times by a much bigger sword. You know how New Dante managed to stab New Vergil in the chest? He outright blitzed him, plain and simple. If Nero does that he's not going to just pull it out, he's going to downright exceed him in half.