If you need it, depends on what apps you want to use the gpwiz in. If the app can't do everything you want on a gamepad, you'll need a joy2key type app.
AFAIK (and I know very little on Mala), you should be able to do everything without the 3rd party app. I don't know if Mala has a max button per joydevice, but what are you trying to do with the missing 16 buttons? Mame, of course, doesn't need the app, and probably preforms better without it.