At home I always sit. I don't care how well endowed you are or how well you can aim, there's always a bit of splash that I don't want to deal with. In most people's homes I'll have the same decency to sit. Nobody wants to sit where someone's pee has been, or clean that off the floor, etc. At work I'll usually sit too, let's be honest I'm probably going to scroll on my phone for a minute or two while I'm at it.

I rarely go to the bathroom in public, I'll usually wait until I get home. For the few exceptions, I'll almost always stand. Because some of those toilet seats, especially in men's bathrooms, can be nasty.