Two different scenarios. It's not like they were in a CQC deadlock and then Garp suddenly gained the upper hand. They just started off by throwing big moves at each other, unlike Kizaru vs Rayleigh. In a similar setting, even MF WB reacted to and almost stabbed Kuzan. It's not something Rayleigh couldn't manage if it comes down to it because he has enough speed to keep up with a faster admiral—Kizaru should be faster than Garp too by the way. The only difference here is Garp and Kuzan are going all out while Rayleigh and Kizaru confined it to just CQC.
In a similar setting MF Whitebeard got the Boundman vs Katakuri treatment by Kuzan. So Garp's feat is objectively superior.
You're right about the CQC point, but even if Rayleigh could do it, he didn't do it, which is gain an upperhand and he had a lot more time to do it. So right now Garp is sitting with the superior feat at a glance. The only angle I can see here is Kuzan could have been wavering vs Kizaru being indifferent.
He also did better with the rescue too because he properly rescued Zoro at point-blank range from a much superior fighter while Garp had to sacrifice himself to do the same. But the circumstances matter, so we can't really say Rayleigh's feat is superior here just like the Garp-Kuzan thing.
Except Garp's rescue had to come when he was already engaged with Kuzan beforehand.
If Rayleigh was already engaged with Kizaru and Zoro was about to be stabbed by Shiryu in the corner, then we'd be talking.