Boomstick: Raiden(MK), while much faster, didn't have the strength necessary to kill the other Raiden. Metal Gear Raiden usually activates Ripper Mode after having taken a lot of damage, but normal Raiden didn't have the strength or electrical voltage to do said damage, so Raiden(MG) wouldn't really have a reason to activate Ripper Mode. The other Raiden did as he stood no chance at winning while he wasn't in his Charged Raiden form.