I think that Brofist from dbz forum made a good point about it when I created such thread:
I think one of the deciding factors of Kaioshin being stronger is Piccolo's own notion to Goku.
Once Piccolo gives up, Goku is basically like "He's that strong?" Not exactly those usage of words but Goku's clearly asking if Kaioshin is stronger and Piccolo admits to that. Goku doesn't recognize the importance of deities. He is clearly asking a question based on strength and power as is typical of Goku and getting admittance to the fact by Piccolo.
It helps also that throughout the series, people make their presence known from their strength. You know, God/Kami wasn't revered because he was a god, it was because he was (at the time at least) strong. He was stronger than Popo who was stronger than King Piccolo. People didn't fear Freeza because he had an iron grip over the galaxy. It was because he was naturally strong. Even a straight up God like Beerus is admired because of his intimidating power and not so much because of his purpose.
If Piccolo was only concerned about Kaioshin's status, his reaction should've been far more subtle and respectable. He doesn't have to look like he's going to piss himself in fear. He can show a little surprise and then step back. He can explain to everyone that this guy is one of the most important people in the universe and show that admiration for him. There is no reason I feel to make Piccolo break down in what almost looks like fear over a guy that Piccolo isn't even entirely sure is a god.
The more apparent reason in the manga to which Piccolo forfeited not being power related and being soemthing he didn't even know, but still leaning towards Kaioshin's identity doesn't make his claim of Kaioshin >> himself invalid or anything like this... they aren't necessarily mutually exclusive. And whilst it got kind of up into the air whether Piccolo told Goku that Kaioshin is >> himself simply because he was really outclassed or in order to get Goku off his back, we have the Daizenshuu clarifying to us what was left somewhat unclear, with a pretty clear cut and dry Kaioshin >> Piccolo.
Kuririn' statement later on doesn't mean much because Kuririn has no clue about how strong Kaioshin is... he didn't see his demeanor in the spaceship, didn't see his movements against Majin Boo and was as clueless as everyone when this pale divinity was about to fight Boo... he had no way of knowing how strong he was, no way of knowing that Piccolo was above Shin and no grounds to contest Piccolo's statement of Kaioshin > himself. Whilst I agree that the "even" generally is used as a way to tell A > B (e.g Piccolo and Trunks at the androids saga), it surely isn't a comparison between Piccolo and Kaioshin at this point, unless one may think he was assuming Kaioshin was weaker than Piccolo based on nothing.
It may also be worth noting that Kami-sama stated back then that he'd merely be a catalyst for Piccolo's strength and knowledge, meaning Piccolo would still be the trigger to take the decisions:
Whilst it obviously would mean Piccolo had the knowledge that Shin was a very important deity, I think it's kind of a stretch that Piccolo's behaviour would be a lot influenced based on that.