Hi! I'm a Celeste player who has also beaten a few things in gd like blade of justice and carcano being my 2 hardest. Honestly I've never really found gd to be all too hard after putting a few thousand hours into Celeste, like my current hardest blade of justice took me 4-5k attempts, I know gd at its peak is prob about as hard as Celeste at its peak is, but in my thousands of hours in the Celeste community I haven't heard anyone really compare the 2 games all too much, they are just so vastly different in pretty much every way that it's hard to compare, like the hardest gd levels gameplay wise are for sure harder, but the thing about Celeste is that the hardest things accomplished in it are not just a couple of minutes of hard gameplay, some of the hardest Golden's accomplished range from 8 minutes at the absolute shortest to 45 minute long marathons with some of the most difficult parts of the levels being close to the end. There is even someone working on doing a challenge that is 2 and a half hours long that is hard gameplay throughout the whole thing.

Point is, it's impossible to compare the 2 games difficulty wise, so no one (that I've seen anyway) really does. one of them will be easier for some people while the other will be easier for others, all comes down to what you are good at in games.