The guy with 70ping has an upper hand since he sees and shoots you 70ms earlier given he didnt miss, but now a days it depends on the game you play, if its any of the recent games with client side hit registeration you'll both exchange kills if you both shot at each other on your screen as you came in contact without missing (Arma Series for example) however (BF4-BF1 excluded -low pinger gets the kill despite you hit him on your screen.