well he certainly decreases his life span everytime he uses that move, but is it draining from everytime he;s killed or everytime he activates it is the real question here(because if its the second it doesnt matter how many times he's killed after he activates it).
For those of you who think Vergil needs to use his Devil Trigger think again. Vergil's base swordsmanship is far superior to Kanda's. First and foremost Vergil practices Iaido style which emphasizes sword-drawing techniques. Drawing a sword from the sheathe, to make an attack that is both quick and powerful is superior to a technique used by a swordsman who fights with their blade at the ready.
Not only that, but as we've seen via Vergil's Dimension Slice, he doesn't have to be anywhere near his opponent to cut them down. With his base strength alone, NO DT, Vergil is able to cut through dimensions and create a vacuum to slice his opponent even if they are yards away from him. And as Beowulf found out the hard way, Vergil can slice his opponent in pieces before they even realize they've been cut. He is that fast.
Japanese legends tell stories about the likes of Jubei and Musashi who could send their opponent to the next world without them even realizing that had just been slain in battle. VERGIL is THAT type of swordsman!
Just on their basic capabilities Vergil would run circles around Kanda.
That's still not counting the fact that Vergil can summon swords to either surround himself as a shield or use them to as projectiles.
Kanda may be able to revive from grievous injuries but there is a limit to the number of times he is able to do that. Vergil, not so much. Vergil wins this without breaking a sweat.
[Suggestion: Maybe the only people who should respond to these threads are those who know enough about the characters who are fighting.]