From what I've read, another major difference between Shuttle and Buran was that the Buran could fly remotely.
The Shuttle must be manned to take off and land.
The ONLY flight of the system was unmanned.
With all their experience in long-term space habitation, they couldn't copy the US life support system as well. Sad.
That, and the capacity to carry several extra crew members. I'm guessing they would have been "political officers" who could make sure the Buran was piloted to a landing on the correct runway, so to speak.
(steely)
IIRC, the Shuttle can do both autonomously. (Indeed, it takes off autonomously every single launch.) Autoland capability exists as well. The astronauts, however, are naturally reticent to allow it.