Twitter to be honest. I'm no fan of Reddit but I can find groups that are fun to participate in. With Twitter I don't have an account and whenever I check on a Tweet I end up regretting it because Twitter is full moronic leftists and enablers.
Twitter is where people go to sniff their own farts. Reddit is where people go circlejerk while sniffing their own farts.
Both are shit but I'm going to have to go with Redditors. It's far easier to create a circlejerk on Reddit and Redditors seem to be in denial about a lot of things such as the fact that they aren't a top-secret internet club and that the overwhelming majority of subs are clearly biased.
I'd go Twitter. Its influence is greater than Reddit's, and Reddit's little groups of decency are much easier to find than Twitter's. Both are mostly terrible, but Twitter also encourages cults of personality and fandom that get all over the site in ways Reddit loonies could only dream of.
Pretty much any popular tweet has a comment section full of the most angry people imaginable just screaming into the void. It's a shame the word 'toxic' has been so overused by faggots because it's the best word to describe it. Redditors at least look like they're having fun, especially if you stick to small subs about niche hobbies rather than just going to the major ones.
Considering the fact that at least 50% of the content of modern reddit are twitter screencaps that get awards after awards by retards who like to waste money over nothing, i'd say that redditors are like the kid in highschool that befriended and costantly licked the ass of the popular kids to be popular too. So redditors not only are uncreative and irrelevant, but they enjoy being it too.
Though both are majority-populated by fart-sniffing circle-jerkers, Reddit has individual subreddits that have the potential to be useful. A handful actually are useful. Twitter, by design, is completely useless for anything other than narcissism and fart-sniffing circle-jerking.
Really depends on where you look, and what you're looking for. If you go looking for shit, you will find shit. If you go looking for good things, you'll find good things. Too many people on here, and among other places that participate in "Cringe Culture," if you will, will only find the negative aspects in things, because that's what they only intend to find.