The right answer depends
1) If defeating Langtry is his mission, then the sword will grant Michael enough power that victory is a reasonable, but not certain, possibility.
2) if Michael is just using the sword for his own ends, the sword will provide no benefit and obviously Langtry will win assuming that Michael does not achieve total surprise at point blank range. (who would expect a knight of the cross to attack to take down Langtry with a surprise sucker punch...)
3) If Langtry is dark/evil (not the case), but fighting Langtry is not Michael's mission - then most likely Langtry would win as he is freaking scary and the Michael would not get the extra "balancing" power a true mission grants.