Yeah, thats probably why they're supplying it on 2 HDD. You have to swap HDD when you want to use DIS vs SSS, I think.

I was just curious what exact interface I need for using the SSS, just in case I ever wanna try that way - on the X or newer BMWs.

I think the optical interface (OPPS) is supposed to be much faster but not sure if that actually would work on the X or its only for the newer BMW models. I assume its only for the newer BMWs.