you certainly have disadvantages because you can't anticipate your opponents moves very well. For example, you sometimes don't see a blue stance lunge move coming or a dfa until it hits you in the face. Also aiming the swings, especially red stance becomes more difficult. Oh, dodging kicks as well, if the lag is "timed" correctly, you find yourself lying on the ground and you didn't see the opponent's animation at all.
But it depends somewhat on the tactics that you are using. If you play blue-stance-quick swing only or pull/backstab, you won't notice very much probably.
As for advantages: just the opposite of the disadvantages. E.g. in a laggy game, use kicks a lot, they are easier to perform (for they are more difficult to dodge, duh.) Also you can "teleport-hop" around the map (as ArtifeX put it
) and thus make yourself more difficult to hit, especially for gunners.