Western tank design selected the heavy/expensive (German) philosophy after WWII. While the East continued with the T-34 philosophy, which worked brilliantly in WWII, but has obvious weaknesses. Now, they've finally accepted the problem and are correcting it:
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The Armata's Vacuum-1 sabot reportedly has a 900mm penetrator, and with a gun whose muzzle velocity exceeds that of the Rheinmetall. This finally matches NATO tanks in firepower. Plus, because the size has now increased it probably has equivalent heavy armor as well (and with all of this, the cost has also increased.)