Thanos, because you don't need to breath to snap. Also because Thanos is cartoonishly strong in a way Anakin is not. If it was Thanos without a magic glove that can do anything, Vader might have a chance.
Last scenario, Vader just might have enough anger and power in him to quickly overpower Thanos by either using force push to pin him to a wall or ceiling, or bringing him to his knees and sliding Thanos towards him, fingers/arms all spread out as Vader ends him in two quick movements first seperating Thanos' glove/arm and flipping around to sever his torso diagonally.
Once this is done, Vader, now walking over Thanos' lifeless body, picks up the glove using the force and guides it over his robotic arm basking in the pain of it's explosive melding of both his skin and suit. He falls to one knee, "Aaahhh"... Smoke is now rising from his broken shell, and looking though a hole in his helmet, eyes red as the sands of Korriban, he raises his hand and snaps...
Everything turns white... a bright white some might even consider, unnatural... yet slowly but surely Anakin can feel his eyesight return... "Wh-... where am I?" he asks as he opens his eyes. He awakens in a field of flowers strangely familiar. As he looks up he sees her... Padmé, standing a few feet away smiling... "Hi Ani."
Edit: Here u go.