PC competitor is shit when used with emulators. There is a lag in response and it doesn't feel right. I bought one a couple of years ago and it was okay for playing simple games but not intense games with detailed control. winUAE had some problems with it but I helped Toni sort them out.
The 4-player adaptor is the way to go. Fully supported by most emulators, no lag and dead easy to built or find in eBay. Supports 2 buttons (use the diagram from the PPJoy drivers website) and only disadvantage is that it does not include +5v connections which means no Autofire if your joystick has one.