DMS said:their best tanks.
The obvious answer is probably best here. In an all-out war, the Soviets have the initial advantage but that will change fairly quickly if the Allies shift air units from the West and go into mass production of the Pershing. The Soviets are far more fatigued from the fighting than the US. So the prior political question is how far does Stalin think he can push before he risks a sustained conflict?
THe best tanks can be blown up by air, so if they attack in the summer, the allies have enough of an air advantage to balance the effect of the greater soviet armor.