Twinswords has longer turn frames, higher reaction time, and no dq. Close to all TS games are won by points and not DQ outside the dojo, which isn't farming. Instafeet is different from left knife as it's harder to kick then punch, and you can't move your feet as fast as your arms. With an instagib knife, you just rotate chest left and contract pecs and BOOM, implosion, DQ, match is over in 3 seconds. Because it's so much easier and faster, it's more commonly abused and is therefore a farm mode.
EDIT: Delaid and CMon beat me to it.