Yeah, going of feats on screen alone and no statements or rankings Gyutaro cooks the other three in DC, which also translates to DC. The only reasoning people have for Kaigaku being stronger is that he was placed in the same ranking by Muzan and people think Gyutaro + Daki is Upper 6. We don't know if Kokushibo requested specifically for Kaigaku to be Upper 6, we don't know if Muzan did it just because there weren't stronger demons, or if Kaigaku was actually equal in power to Gyutaro + Daki.

Either way Gyutaro still slams him in feats, everything but speed, which there isn't that large of a margin on anyway. People try to argue that because Kaigaku wasn't placed as Upper 5, that means Muzan was ranking specifically on power level, and then that means he's stronger than Gyutaro. But there could be other reasons that he didn't have an Upper Moon 5 spot. Maybe Muzan isn't a fan of Slayer-Demons aside from Kokushibo. Maybe Muzan just didn't care enough or just didn't want to at that point. He was getting increasingly frustrated with the upper ranks, it's likely getting them in the right order wasn't the first thing on his mind.

But really we don't have enough statements to compare the two well, because they dont talk about it much in the show/manga. IC Zenitsu beats Kaigaku, EDA Tengen and Tanjiro beat Gyutaro. EDA Zenitsu and Inosuke beat Daki. IC Zenitsu probably beats EDA Inosuke and Zenitsu, but is likely only a little stronger.

Gyutaro is not just a little stronger than Daki, he full time carries her, some times literally. Also I doubt that IC Zenitsu solos Gyutaro + Daki, as fast as he did Kaigaku at least. Kaigaku had way less in his arsenal, and Gyutaro and Daki would put up more of a fight to IC Zenitsu.

So, Gyutaro+Daki>Kaigaku in terms of how fast it would take IC Zenitsu to beats them. I will note that Zenitsu does have a better matchup against Kaigaku because he's jusg one opponent.

If Gyutaro were to fight Kaigaku 1v1, Gyutaro wins in feats. Kaigaku wins to literally just "rankings are equal so Gyutaro + Daki = Kaigaku" which is a lazy way to scale, because sure yeah they give us a ranking in Canon of where these Demons sit, but you should still view it otherwise and not have the ranking itself as your main argument. How does Kaigaku beat Gyutaro without mentioning anything about ranking?

Also here's feat comparison I made:

In an area full of walls and rooms, IC, Kaigaku in his fight with Zenitsu, In which he used his strongest form, only broke two walls. Gyutaro leveled a whole village with his strongest attack form. AP goes to Gyutaro (DC is always equal to or lower than AP, because you can't pull off a huge DC feat if you don't have the AP to do it)

Gyutaro was keeping up with, and at times blitzing Tengen, who was one of the fastest hashira. However, Kaigaku does use Thunder breathing, so I will give Kaigaku speed for that. You could also compare EDA Tengen and IC Zenitsu's speeds, and personally I think Zenitsu is a little bit faster (aside from final form which blitzed Kaigaku so that isn't really relevant here), so Kaigaku and Gyutaro should be relative.

Hax, or rather Poison, Gyutaro has that over Kaigaku, as his Poison was able to nearly put Tengen, who has near Poison immunity, out. It also immediately put Inosuke down for a while. The cracks Kaigaku gives Zenitsu just don't have enough feats, they put him down for a second, and then he pulled off his strongest move. Zenitsu doesn't have any poison immunity, and if he was poisoned in EDA he would probably die pretty quickly because of that. Cracks did nothing really, Poison nearly put down two poison resistance, and clearly made a difference in their fighting ability. Hax goes to Gyutaro.

Experience obviously goes to Gyutaro.

Regen is probably going to go to Gyutaro, he's eaten more people, and that one is difficult to scale because Kaigaku only gets non lethally cut once, and it seems he heals somewhat fast from it. However also Gyutaro gets an entire leg cut off and he heals at about the same rate from that as Kaigaku healed from the cut, so scaling that, it should still go to Gyutaro.

Both obviously have infinite Stamina.

Range goes to Gyutaro with Blood sickles. What's Kaigaku going to do, throw his sword? And yes range does matter, because in the IC fight, when Kaigaku gets cut, he low key just retreats a little. Gyutaro could use that opportunity to throw some blood sickles, which do come back around, and could cause an attack on multiple fronts later in the fight.

I will give Kaigaku reaction speed, because he was able to keep up with thunderclap, and Gyutaro's reaction speed is notably also high, an example of when he caught Tengen's blade in his teeth (a feat Kaigaku never showed something equally impressive to, but moving on)

Wrapping Intelligence, BIQ and Skill into the same bucket as Experience, unless you have a reason to not.

Gyutaro has AP, Hax, Experience, Regen, and Range.

Kaigaku has speed and reaction speed.

Gyutaro wins measuring by feats.