The interesting thing about "vorpal" swords is that, if one actually looks at the only source material for the term, one will see that it does not describe the D&D type of "vorpal" (cuts real good and decapitates).
One, two! One, two! And through and through
The vorpal blade went snicker-snack!
He left it dead, and with its head
He went galumphing back.
From this description, a stronger case can be made that the vorpal sword is primarily a thrusting weapon--and not necessarily the most substantial thrusting sword, either.
"One, two!" is obviously a reference to the "one two", a type of preparation used in modern fencing and its ancestors, perhaps as far back to the rapier, depending upon which interpratoins of sources one believes. The "one" refers to initiating action in one "line" and "two" refers to changing the "line" before actually attacking.
Then we have the phrase "and through". To if one were to "run" an enemy "through", it means that one has
thrust ones weapon in so deeply it comes out the back.
Finally, a sound or action associated with the vorpal blade is "snicker-snack". This is obviously onomotopoeia for the sounds that Prof. Dodgson would have heard from young gentlemen practicing fencing (with thrusting weapons) in his own day, and it would be most typical of the sort of attack and defense one would expect to be most likely for a lighter thrusting sword.
That the beast's head was ultimately removed says nothing about how the vorpal sword works, since it was never said that the head was removed
in combat. Indeed, it would make just as much sense for it to be removed after combat, as a trophy.
Thus, instead of being some great brutal cleaver, the vorpal sword may very well be a light, lithe, thrusting sword.