originations is what it comes down to. i'm scottish rite, but not york rite, so my explanation is more about "what the scottish rite IS" than "how it compares to york rite."
reading "a bridge to light" will explain what you will experience in the scottish rite dramas very well. as a matter of fact, you'll get a copy when you go through the degrees (if you do). effectively, it explains everything that you'll learn in the scottish rite. trust me when I say this, however: it's the same as if you simply "read" the blue lodge degrees. it will mean so much more if you experience them as a witness on the sidelines. (you are part of an audience during the scottish rite degrees, rather than the actual candidate... in texas, we do the 1st 3 degrees in the york rite tradition, rather than the scottish rite tradition... go to louisiana if you'd rather experience the scottish rite EA, FC, and MM degrees- IIRC).
as far as the basic "storyline" goes, the 4th degree starts out with what is happening in masonry RIGHT AFTER how the master mason's degree ends, and continues "through history" to more or less present day. the lessons continue through the Caballistic tradition up until the "grand encampment" which ties everything together in the "Master of the Royal Secret" degree.
i'm assuming you are a mason. this will mean something, then. "what was lost, is now found." sorta.
think back to the drama, when KS announces that he's approaching you... and what he has to say. it completes that part.