I've hacked both keyboards and gamepads. The gamepads both took longer, are less functional, and cost more, but the differences arent' that great.
If I were in your situation and I wanted to interface a one or two joystick panel to a PC, I would use a keyboard hack. Especially if you can find an old IBM AT style keyboard in a thrift shop for $2. I can send you the encoder matrix and save you the time of figguring that part out.
The mameworld link in a previous post is mandatory reading before trying a keyboard hack.
Bob