At Palmdale Airport they have a display of a SR-71 and an A-12 next to each other, as well as a D-21 Drone and a U-2. This is the only place I know that has both aircraft next to each other, making the small differences much more obvious. The A-12 predates the SR-71 and wasn't made public until 1981, long after it stopped flying.

* Actual speeds and flight ceiling are classified, so, maybe the SR-71 can go higher and faster but they can't tell us.