They look fairly similar to me, although I hear a very different tone. In trying to teach this technique to people, I've discovered that most people end up using a slightly different technique because everyone has different shaped thumbs, so it might be that you end up with something different from both of them!
I think their basses have very different tones from the get go, which might account for a large amount of the difference. I think that Victor also has a different touch on the string.