I pick it up probably 98% of the time. Use a fork and knife only if it’s a specialty pizza with a bulky topping like chicken marsala.
Like you, I’m a New Yorker and will sometimes fold. If you order by the slice at a pizzeria, it’s often too wide to handle without making a mess, and folding is necessary (or you have to use two hands). Because the pie they make to sell as individual slices is larger than the one you get if you order a full pie for takeout. (Anyone from the NYC area knows what I’m talking about.)