Well, with the printer switch, you would have your controls connected to the output side, and your Ipac connected to input A, and your Xbox 360 to input B. Then, with a simple flip of the switch, you would change which system would be active. (As long as you are consistent in wiring sides A & B, for example, pin 1 for both would need to be the same button or direction, and so on...) That's one solution to your problem.
The other solution you mentioned, the DB-25 connectors, would require you reaching in and plugging in the desired system (while unplugging the inactive system).
Hope this helps. I could come up with some quick diagrams to help you visualize, if you want.
-Lee