I highly doubt that, the rules were very different in PRICE vs UFC plus ring vs. octagon.
If PRIDE was around and UFC folded, I would be willing to bet guys used to the octagon would have very dismal showings when they transitioned over to the ring (+ head stomps and soccer kicks).
Not saying there wasn't PED abuse in Japan, there clearly was (but I highly doubt with these 2 legends).
It's got nothing to do with the rules, which is a valid point.
Both those guys looked pounds lighter in Pride. Their overall body movement was far more dynamic. Both these guys came to the UFC, and have since looked like they are fighting in slow motion compared to their Pride days. Is that not how you see it? Maybe I need to go back and watch some old videos. My memory might be somewhat hazy.