Keyboard.
To the extent that one of the requirements for buying a new laptop or keyboard is explicitly that no locking or ghosting occurs with Shift-Z-X-C-Ctrl-Arrows and that they're of sufficient size. Even moreso, to the extent that I am in the void phase between planning and building an arcade stick that operates not with a stick, but with mechanical keyswitches that are placed in positions accurate to a keyboard. I could probably make do with a gamepad if a particularly nice one fell into my possession, or an actual stick at that, but as of now there isn't anything I feel comfortable playing with.