They're all harsh in their own special way. It's hard to quantify.
4chan is in bed with SJWs so you're not allowed to make them look bad.
Reddit has a strict definition of "doxxing" so they can't even do things like ODN. Not that anyone's doing ODN anymore anyways. But they don't give a shit how off-topic threads are anymore so you can start a thread about anything if you can somehow find any kind of connection to how it's related.
GGHQ is involved in a hissy fight with revolt so you're not allowed to act like revolt. But unlike KIA, you can actually do things like ODN on here. Not that anyone's doing it.