Mig-25 vs. SR-71 and XB-70 vs. T-4

These four aircraft are arguably the fastest manned jets ever built and were also designed in response to one another in the Cold War. The question is: which superpower created the better aircraft: the Soviets or the Americans. For the Mig-25 vs. SR-71, I believe the Blackbird edges out the Foxbat for speed, especially sustained speed. But, if the Blackbird were still in service, it would be pretty hard for it to get by the Russian border, as the missiles on the Mig-25/31 have improved. For the XB-70 vs. Sukhoi T-4, again, the Valkyrie edges out the Sotka in speed and definitely range. First of all, the T-4 was never flown above M1.3, so how believable is the M3 speed the Russians said it had? These are four fantastic aircraft.
What are your thoughts?