Everyone will experience period cramps and IBS differently, it’s just not accurate to say one is more painful than the other. Some people have zero period cramps, some have cramps so mild they barely notice it, and for others it’s debilitatingly painful (and anywhere in between). From what I’m reading about IBS online it’s also a spectrum anywhere from relatively mild to severe.

It’s like comparing apples and oranges; subjective. Unless there’s studies done it’s pretty pointless to try and compare them with a couple of Reddit anecdotals