This question always comes back, soviet state decided to produce 3 tanks that are arguably totally equivalent, but in the same time, very different, with a problem in logistic.
The T-64 was produced in 8000 pieces, the T-72 at least 20000, the T-80, at least 5000. These tanks were to replace the previous generations, the T-54 and T-55, based on 1944 design... And T-62, just a modification of said design. Also, the T-10M was to be replaced by the new gen tanks.
T-64 as we all know, was a breakthrough in all aspects, firepower, mobility, size, armour... Once perfected, it became the main steel fist of the soviet army vs NATO. T-72 was a concurrent design, and was accepted by the state because it had many things going for him: it was easier and cheaper to produce, it could be exported and used to equip allies nation of the warsaw pact, it had a proven and reliable engine, while keeping most of the T-64 performance. T-80 was originally just a T-64 with a new super engine, a gas turbine. Later T-80 was accepted along the already existing T-64 and T-72, a choice dubious for a state already manufacturing 2 tanks, and mostly a political move. But the T-80 was also perfected, and found to be a great machine, exeeding T-64 in most ways, and the thinking then was to replace T-64 with T-80 and to keep T-72 for the export market and low-end domestic use.
I found this website in russian, which makes a great comparative of the 3 tanks, and the T-72 finally comes out best.
In this battle, they compare the main and most common in mid 1980s variant of each tank, namely the T-64BV, the T-72B and T-80BV. All these tanks are covered with 4S20 Kontakt 1 ERA.
With their point system, the T-72B takes 1st place, with 137 points, the T-80BV is 2nd for the sake of it, but it's simply equal, at 135 points. The T-64BV lags behind, at 124 points.
T-72B (Object 184): 1985
T-80B (Object 219R): 1978, BV (Object 219RV): 1985 (possibly earlier)
T-64B (Object 447A): 1976, BV: 1985 or earlier.
I haven't fully read the source