These are two stunt doubles you have to figure are just bad to the bone. Putting them in even a mock knife fight looks like it would be absolutely brutal, not to mention impressive. Each woman is skilled at their craft and knows how to disarm and disable the other, but it would seem that the stunt woman for the Black Widow is a little more crafty than Elektra’s stunt double.
For one thing she goes for function instead of form while Elektra is more flips and acrobatic moves that are pretty but not exactly practical. Black Widow tends to go in for the kill first and worry about looking good later. This is the real deception between the two, Elektra is known for being a world-class assassin, but her reputation preceding her isn’t always a good thing. If she comes up against an opponent that is equally or better skilled it makes her look like a bit of a novice when she’s taken down or taken out.
Black Widow on the other hand has been taught to fight in a more functional manner. While she can execute the flips and grander movements that Elektra does she eschews them for the simple and effective movements that give her the edge. There’s less grace to what she does and more of a street-fighting mentality that allows her to get the job done and call it over before her opponent really knows what’s hit them.
Knife fight in the movies and on film are often played up to look cool and offer a lot of flashy, deadly movements that make people believe that this is real and could possibly take place. While the answer to that is yes, this could most definitely take place, the truth is that the average knife fight can be over in as little as a few seconds. Even with two highly skilled combatants such as these the margin for error is frighteningly low. In a real knife fight it is far more likely that at least one of them would have been wounded if not worse.
The stripping away of the knives is a little suspect but it still believable enough to pass muster for now. When Elektra is the last one with the knife however it doesn’t stop Black Widow simply because she has been taught how to take the weapon of her opponent and use it against them. Barring that she is taught to disarm, disable, and defeat her opponent. And to be quite honest that’s what she does. She stuns Elektra first and then takes her down in a non-lethal manner that allows her to effectively disable her opponent.
It’s hard to see a favorite go down in such a fashion, but in all honesty there is room to believe that Elektra would not be as quick as Black Widow to lower herself to the street-fight mentality. As an assassin it seems kind of hypocritical to worry about such a method, but in the comics she’s almost always been stuck on doing things in a more flashy manner rather than just digging in and bulling her way through an opponent.