Something happened there. For Vegeta to lose most of his energy and 19 to be the benefactor of that, it suggests that 19 should be stronger than Vegeta or close at least. I think ripping off the arms made 19 lose power or just freak out completely or something, I don't know.
Are you trying to tell me that Sick Goku wouldn't be whooping Gero?
Now that I think about it, yeah, it's a tricky situation. #19 should be a beast after absorbing that much of Vegeta's power, yet is implied to be below #20, somehow... Even before ripping off 19's arms, I think Vegeta should be stronger, since he was able to do it.
Unless #19 lost a lot of power over Vegeta's beating?
Oh as in he lost a lot of power leading up to it? That's quite possible. That's probably the answer. Let's say 19 has gone down to 75% of his power he had initially against Vegeta, that's quite possible I think. And then absorbing all of that power from Vegeta and still not being strong enough. Vegeta is probably not even that much stronger than him either. He loses a little power with the Big Bang Attack and that's how 20 can easily beat him I guess.
Let's lock this thread, it's been proven without a shadow of a doubt that Piccolo can indeed beat 19 Post. I was wrong.