R37 is way faster, more appropriated to intercept low observable assets and AWACS, tankers, it meant for intercepting low observable assets like F-35/F-22/B-2 and B-1the question is what is the use of R-37m if it only can get lock on tanker size target at 100km, r-77 is capable enough if you want hit
R77 had poor performances for exemple in the Pakistan India skirmishes, they gone to the Israelis to get I-Derby ER missiles instead of R77 export