Tap jump off please. It does lead to accidental double jumps when you're trying to Uair, and sometimes accidental jumps when you're trying to Utilt from the ground.
Also, Button jump (with x, y, z, r) is probably the easiest way to perform consistent short hops. I don't think I need to explain how important short-hopping is in SSB, SSBM, and SSBB. Button-release and sensitivity to X/Y is easier for me than using Z, but I imagine L or R to be just as good (since there is so much physical button-depth on button presses for quicker button release)
Short-hopping takes practice if you're not used to it, but it's all about quickening your button release (with X/Y/Z) and button press sensitivity with L/R.