I think I am on Piccolo Daimao side here
Chapter: 472 (DBZ 278), P9.4
Context: after explaining that Fusion lasts 30 minutes
Goku: “With these two, if they just manage to perform Fusion successfully, I think they’ll definitely be able to defeat him within 30 minutes. Fusion is just that extreme.”
Goku was speculating. Since Goku can't predict the future, his statement doesn't prove anything.
Chapter: 477 (DBZ 283), P11.8
Context: Chi-Chi thinks Goten will get killed by Boo
Goku: “Don’t worry. If he perfects the technique he’s trying now, he definitely ain’t gonna lose.”
Same here, Goku is guessing what will happen.
Chapter: 482 (DBZ 288), P7.2-3
Context: after Super Saiyan Gotenks forms for the first time
Piccolo: “…Yeah…Your ki really is absolutely incredible, but how about your movement?...Show me a little”
Gotenks: “Is that alright? If I show you here, the house might break. I’ll do it on the ground.”
Gotenks Ki surely is incredible. But this tells little about how his power compare to X character.
Chapter: 482 (DBZ 288), P9.3-8
Context: Piccolo finally catches up to Gotenks
Gotenks: “You’re slow. So you finally got here? Besides circling around the Earth several times, I even took a little afternoon nap. [ ] Fuffuffuh…So you can’t tell just from my speed just now? My super-duper incredible power…! …Which is to say that the test is over, and I’m going to go take care of that annoying Majin Boo right away…”
*Gotenks takes off*
Piccolo: “H-hey, you idiot! Kuh…! Wh-what a shithead…H-he already has only 1 minute left that he can stay merged. That dimwhit…!”
At first Gotenks thought he could take Boo without even going Super Saiyan... you really can't trust Gotenks judgement. In fact every single time Gotenks said he could take his opponent with his X form, he was very wrong.
I don't really see anything here that serves to compares Gotenk's strength to the fat Majin Boo.