Playing Amiga games with a gamepad is simply an inauthentic experience. Only a console gamer could assert gamepads are superior to a joystick.
I'm running a Logitech "Precision" Gamepad and a Competition Pro, and find the latter far superior. For instance, the gamepad is too sensitive when waggling in Xenon to transform from tank to jet, which means you transform accidentally. This rarely--if ever--happens with a decent joystick of any kind, in WinUAE or on original hardware.
Also games which require sensitive diagonal movements are all but useless using a gamepad. And if you are a purist, and don't utilise auto-fire, whether you use your thumb or invert your hand and use your finger on the pad matters not: you cannot fire like you can with a decent sized trigger.
In short, sticks >> pads on Amiga. To assert otherwise is foolishness.
(Oh, OT: try playing Raiden on MAME with a gamepad, lol.)