Alright, took apart the “SLS” pad I got from focalprice. Looked at the PCB, looks legit based on the litanedup ebay page pictures.
I also took the liberty of taking apart my original saturn pad…the designs are almost identical in every way. The only discernible difference is the shoulder buttons - the saturn shoulder buttons make contact with a clicky button by purely plastic. The SLS pads do so by a rubber extension, as it appears the original saturn buttons didn’t quite reach far enough. As a result, the shoulder buttons aren’t as good as they should be. Aside from not being as clicky, one of the SLS shoulder buttons appears to be a little large somewhere, as it fits more snugly then it should.
Other than that, every part appears to be interchangeable. I decided to replace the saturn PCB with the SLS usb pcb in the original saturn casing with buttons and all (except the shoulder buttons, which I had to use the SLS ones for) and give it a shot.
Impressions: The saturn pad with the usb pcb feels a lot smoother. The SLS d-pad is jerky by comparison. The saturn d-pad is more responsive, and the buttons feel a bit better too. It seems like it might be because of the silicon pads used (i kept the original saturn ones in there).
Now I’m going to have to buy 2 more saturn controllers for my sega saturn…I made the SLS pad a sega saturn controller but I want the real thing…unless someone can suggest a place to get other silicon pads used for the buttons.
Results of this experiment:
-It is now $15 (focalprice) to turn a REAL saturn pad into a usb pad (sans shoulder buttons…but those aren’t terribly vital)
-I now lost a good pad for my sega saturn and need to buy 2 more…but on the other hand I have an extra controller suitable for saturn bomberman!
I guess it’s important to note the SLS pad (at least in this instance…maybe i didn’t get a great one?) isn’t bad. It’s pretty good compared to other controllers. However, if you were expecting the fluid d-pad from the original saturn pad, you’re probably not going to get it.
Now…time to stop screwing around…I have 2 midterms to study for 
UPDATE: I took apart the controllers again and put everything back, but I swapped the pads used to make contact between buttons and the pcb. There isn’t much of a difference, but after having used the SLS usb controller in it’s normal form for a while, it seems like burning it in by playing more will make the d-pad feel a bit smoother, I hope.