SR 71 vs U2: Which one is better?

that depends on the mission requirements, and what defenses are over the target. both planes fly above 80,000ft, but the SR71 flies faster than mach 3. if you need to get in and out quickly, then the SR71 is for you. if you need to loiter then use the U2, now designated as the TR1. understand on thing though, at high altitude the U2 has an 8-12kt speed range which you must be in otherwise you either stall the aircraft(speed below 400kts), or break the aircraft(speed above 412kts).