USB Saturn pads generally have better D-pads than most 3rd party controllers.
Most pads that have wired-USB cords function with PS3… You just have to experiment and figure out how to configure the pads properly for fighting games. Generic USB pads aren’t button-configured for fighting games so it’s best to use Practice Mode and experiment there until you figure out which button setups are best for Light, Medium, Heavy, Special, Crossover Partner assignments.
I still think in general that six-button facepads are better. I don’t like dealing with shoulder buttons on fighting games… doesn’t feel natural and they’re harder to coordinate together for me.
As far as a PS-style pad that has a better D-pad than the standard Dual Shock, I really don’t know. Choices for decent D-pads on PS-clones are limited and I haven’t tried any to make a recommendation.
Pelican (PDP) and Logitech DO make PS3-style pads. One of the recent PDP pads was the TRON-licensed pad that has LED lighting. That’s $50, though. ($50 wired-USB, too. Weird and expensive for a PS3 wired pad. Most wired PS3 pads cost $30 or less.) There are other glowing/transparent pads that can be fought for substantially less than that – $30, I think. Can’t vouch for the D-pads on either but build quality should be fine on most pads as long as they aren’t Mad Catz pads.
You’re definitely going to be limited to wired USB pads. Wireless won’t sync with a PS3 unless they’re officially endorsed by Sony and have Sony licensed PCBs. A lot of the Sony PS-clone pads have dongles so they’re not exactly blue tooth, either.
I’d stick to wired USB pads since A) you’ll be dealing dongles and I don’t know if you like that wireless option; B) wired USB pads are generally compatible with PS3; and C) you don’t have to worry about recharging batteries or changing them. Most cords are at least 6’ to 10’ long anyway…
I agree with most people that Sony D-pads stink. It’s always been the bane of fighting game fans as far as Sony system’s are confirmed and in the past I preferred to use Sega pads for fighting games. Now that I’m a joystick modder and connoisseur, D-pads are my second option. Based on my past history and what I’ve been comfortable with, Sega Saturn pad layout is still my pad preference for fighting games.