Pissing is literally the greatest thing in the world. It feels so fucking good to down several billion cubic litres of water, feel it building up in your dick and shoot an almighty hydro pump of golden nectar right into the toilet. I should start urinating on people for money.
On a more (actually less) serious note I love to take those shits where the whole log expels itself firmly from your colon at once and you go to wipe and there's nothing to wipe away. That is the definition of a good shit right there. Because usually taking a shit gives me Euphoria but wiping away my shit gives me Dysphoria.
Shitting is more satisfying but pissing is easier IMO, you can do it any time as opposed to after you've eaten something. It's likea sustained, mild orgasm for me to piss a full bladder.