Aside from small pizzas, I generally cut pizzas into 12 pieces. 8 slices ends up with unwieldy slices, 16 makes for overly narrow ones. Cut it however you want, of course, but for most average sized pizzas 12 makes for a nice sized slice.
That’s very much a cultural thing. An average European pizza is more of a ‘personal’ pizza and 8 or 10 inches in diameter. Twelve slices would be too much.
I propose the Imperial/English pizza theorem. The optimal number of slices for a pizza is equal to the size in inches.
Unfortunately, that guarantees the arc length of the slice to be constant (at pi inches), but not the total area (= d * 1/2 in). I believe this is why larger pizzas make more sense to cut into squares, as long thin pieces are harder to slice and to eat.
Yeah, that's my exclusion for small pizzas. We only do personal pizzas for the kids. The rest of the family shares a larger one (or two, or however many).