Didn't think about it too hard, I use the reset switch (that I can operate with my finger) on my current keyboard all the time, but a key combination would probably be fine as well. If you mess up, and for example flash a keymap that makes it impossible to access the reset key, you'd have to disassemble the case to press the button though, right?
/edit: To explain why I'd want a big one or none at all: If there's a big one, I'll use that because it's the most convenient. If I have to use a pin, then pressing a key combination is more convenient, therefore I don't need a hole at all.