I don't remember it being explicitly stated that "I gave you more power than Cain", rather that seems to be the logical extension people are taking "You're my favorite avatar. Why do you think I've given you so much?" to --Referring to his demon-like form.
Demon Colossus should logically be more powerful. Plus I don't remember Cain ever beating down someone on the level of Rulk so easily, especially with no shield.
If you count 8th Day then they would be comparable. Thor was at least able to mount some sort of offense but I guess you could say he lasted as long as Cain allowed him to. Normal Juggs wasn't that powerful though.
Normal Juggs beat down Thor twice though, with Thor winning both battles through BFR and magic I believe. Thor stood absolutely no chance in either of the fights without bfr's by Mjolnir and dropping Cain's forcefield.
If Piotr can stop having "Bob Ross moments", he would own classic Juggs, it wouldn't even be close.
The problem is that he starts his whining bagpipe and loses focus. If Piotr thought Cain would kill Kitty or had injured Logan or some scenario where he had to protect someone he cared about, he would put Juggs out of his misery.