So what's harder from a pain perspective? In my view, Comrades (90k run) is much harder. OK - maybe I didn't train appropriately for the run, but still, I've never had an out of body experience in an Ironman (3.8k swim; 180k bike; 42.2k run). But then I don't have the Ironman water-death-fear, nor have I ever truly overexerted myself in one.
What it comes down to is this. Ironman tattoos are pretty cool. Lots of colour, imagination and the look is somewhat gladiatoral. Whereas, when I look at the Comrades tattoo (last pic below), it looks pretty much what I'd expect a prison tat to look like. Now that is hardcore. Even if you didn't administer it to yourself with a dirty needle while on a brief spell behind bars for nefarious offences.
Click on the Ironman pic below if you want to see a cool blog with lots of Irontats.