V being entirely human meant he was more in tune with his emotions and, despite trying to remain stoic, he definitely found himself "feeling" more as a human. I think it took becoming human to make Vergil realize that humans are special in their own way.
Vergil definitely only gained empathy after V merged back with Urizen.
V himself deliberately chose to stay in Red Grave City in the month-long interim between Dante losing to Urizen and Nero returning for the express purpose of helping people, at great cost to his already shortened life. V...
After beating him he yells "The power of Sparda... Why won't you give me strength?!". I always took that as implying that while he could wield it, in his hands it was just a particularly fancy sword and didn't lend him any power.
Dante says "bitch" and "ass" at a few points. During the final boss fight, when you use a certain ability that lets the fight continue, Nero yells "**** YOU!" and as far as I can remember it's the only f-bomb in the game.
I must be the only person on the planet who enjoyed playing as V. lol He was the character I looked forward to the most and while I understand why they gave him the least missions of every character because of his unique playstyle, I was a little disappointed.
Honestly most of the games are better than 3 to me. From a purely gameplay standpoint I can't stand more than half of 3's enemy roster. The chess pieces, Fallen, basically anything that isn't a Hell or an Abyss is incredibly difficult to juggle or keep styling on them in general.