When defending your legs while using a two-handed sword (longsword, zweihander, etc), what are the advantages and disadvantages between blocking low vs voiding your legs and counter-attacking?
(Disclaimer: I understand that nothing is strictly better all the time, and that context matters. My question is asked accordingly, and answers should be made similarly.)
I've heard mention that a major advantage of larger, longer swords is their ability to successfully defend the legs by blocking low - something that shorter bladed weapons cannot do. However, this article discussing the teachings of 14th-century longsword master Johannes Liechtenauer appears to suggest that a superior form of defending one's legs is not to block, but rather to threaten a dodge and counter-attack.
So far we have used the Plow guard to defend against an attack to the torso, and we have used the Ox guard to defend against an attack to the head. It would seem logical, then, that to defend against a cut to the legs one would therefore use the Fool's guard, as it lies low. While this is not an impossible thing to do, it is not actually a very good defense, as follow-up attacks from this position will be too slow. The Schietelhau, or Parting Strike, offers a much more efficient way of defending the legs.
One cannot make a cut for the legs without exposing the head. If your opponent attacks your lead foot you simply need to remove that target from reach while simultaneously striking the now-vulnerable head. In this case, blade contact is completely unnecessary, and this reaffirms the point that you should not be chasing your opponent's weapon, but always attack the opponent. The safest way to move the foot from harm is to move it backwards, though you do not want to step so far back that you cannot reach your opponent. Instead take a half step back as you cut. You will want to make sure that your arms stay high for this strike, as you do not want your opponent to make a sudden change upwards and catch your elbows. You will always be able to do this, regardless of how tall your opponent is by virtue of the fact that your shoulders are high and your legs are not. Keep in mind that this can also be done as a thrust should you have started in a guard such as the Plow.
The idea here seems to be that making an attack to someone's legs inherently over-commits and leaves them vulnerable (relatively-speaking) to a counter-strike to the head. Is this a more consistent and reliable alternative to blocking? What circumstances effect this?