I did not see this topic until today. I wonder how many other threads I've been missing?
Anyway, I honestly don't find any differences amongst the standard PCE pads. I've never used the 6-button controllers, nor have I had the RX pad, though.
Anyway, I had been having fun with a generic 3-button PCE pad and the official AVE 3 pad about a year ago, before I moved. It was simply for their novelty, though (I was playing games that used the SELECT button... but I used the THRID BUTTON wooohooo!). Hey, I'm easily amused.
Otherwise, I guess I spend the most time using CoreGrafx PCE pads. I suppose they're my favorites, by default.
EDIT: Ok, folks, tell me about the pad in this picture:
Source pageI've only ever seen this pad
here, where it is referred to as a "Battle Pad".
It doesn't look particularly comfortable, but I'm curious about it. My thrid-party 3-button pad is pictured on the page, look for "PC BLASTER".