I believe there were two generations of that older G80 card and the first one had 96 shaders the second gen had 112, I missed that generation of cards unfortunately.
There might be a little performance difference, and they will have different P/N's, etc, but overall they will get similar performance and in SLI, it doesn't matter. There is nothing you can do to change the lesser card (by not much) to equal the better card but a slight overclock...and really both cards are still pretty capable, so in SLI you should be doing pretty good.
I'd say if you want to know more, do some google searching on 8800GTS 96SP vs 112SP...hell I know there were a few threads created here about them a while back.
Hope that helps!
