4chan has limits on its degeneracy because there is a relatively small number of boards such that anyone could reasonably access all of them (harder to develop an echo chamber) and mods are at most board specific, relative to reddit mods being subreddit specific, which means reddit mods are more likely to allow the crazy to continue in their little corner of the internet as opposed to 4chan mods. My point is that if someone on reddit goes into their uber-niche subreddit for eating their own shit or fucking toasters, everyone agrees with them in their little echo chamber, all dissenting voices are banned, and the idiocy can spiral out of control as nobody is there to point out that fucking toasters might be a bad idea. But in 4chan, generally, you'll have people calling you out for being an idiot, which limits the degeneracy somewhat. I admit the 4chan lingo is far more divisive, but that is just them communicating in the way they know best. It's like calling a cat an idiot for meowing, but not calling a dog an idiot for barking. You need to look past the form of communication to understand if they are degenerate or not.

I'd probably estimate that the median reddit user is more normal than the median 4chan user, but when talking about the small portion of crazies, I believe that reddit has more completely bonkers weirdos than 4chan does.