The aftermarket system is the same as the one that comes on factory model instruments.
On the Xotic effects website Scott Henderson does a demo of the backplate system....it is amazing.
FAIR WARNING...
The Backplate System that comes STOCK/PRE INSTALLED in a Suhe guitar works FAR better than the aftermarket system that you can install (or have installed) into a Fender or whatever kind of guitar. Also, even the stock system pre installed into a Suhr guitar doesn't kill ALL of the hum. It kills most of it (more than 50%) but they DO STILL SUFFER FROM 60 CYCLE BUZZ/HUM and just like any single coil pickup it DOES get worse depending on the conditions...dirty power, neon lights, TV's, computers, etc.
I jus have to pass this info on...this is in no way a slam on the Backplate System, it does cut down on noise but in fairness the name (Silent) is a bit misleading. As for the differences in the pre installed system vs the one you can buy aftermarket, im not sure why there are differnces but I know that there are and have even spoken via email with the people at Suhr AND the actual designer of the Backplate System.
Is it a great system...yes
Does it cut down on noise...yes
Is it silent...NO
Is it useful...it all depends on your personal situation
My personal suggestion, if you need a COMPLETELY noiseless Strat get noiseless pickups and be done with it.
It's one of those inventions that's one of the most brilliant ideas in the history of aftermarket guitar parts. I'm sure even Seymour smacked himself in the head when he saw it.....or not.
It's true you can use any traditional type of single coil strat pickup, but all 3 must have the same polarity/wind direction. That means if you ordered the Suhr system, you'd have to make sure your middle is not rw/rp....just a regular neck pickup.
The first time I saw it being demoed, I was standing next to the owner of Matchless Amps, Phil Jamison, and he was almost angry at himself for not thinking of it first.
Everyone who sees/hears/plays it is blown away by it. All the positions of your strat are virtually silent, with none of the tone robbing properties of noiseless designs. The coil strapped to the backplate on the body cancels out the hum, and you can fine tune it with a mini pot, I believe. It sort of does the same thing as moving your body around, finding the most silent spot....only it's always at that spot!
They're expensive, but if you only had one on your main strat, it'd probably be worth it. You'd have to buy all your pickups with the same polarity, so that'd make it harder to buy/sell them too.