Radio's boost to unit cohesion could by quite big in terms of efficiency.
Due to the difficulty in using signal flags in combat a very common practice was "Do as I do!". A platoon would fire on the target that the platoon leader fired on or simply followed where the PL went. With regard to fire that was not always the worst option. It did mean that a target could get suppressed/killed quicker but at the expense of dealing with multiple targets.
German: A mid war 5 tank platoon would have a PL tank with a transceiver, two sections each with a section leader with a transceiver and a 'wingman' with a receiver for a total of 3 transceivers and 2 receiver. So everyone could receive orders but some could not give back information. As a general statement, every German tank (even reworked captured ones) had a radio of some sort.
British: All light tanks from the Mk VI, all cruisers and all infantry tanks from the Mk II Matilda had radios. Even many carriers had radios. Later in the war they fitted phones on their rear to talk to accompanying infantry.
French: The French eventually started to put radios in their tanks starting with the S-35 and Char B1 bis. However they use Morse rather than voice as they felt the noisy environment inside a tank was not good for voice. In addition Morse usually effectively reaches further than voice for the same power output. The downside is the need for Morse trained operators and the slow data rate compared to voice.
US: Followed the British pattern.
Soviet: Tankettes and light tanks rarely had radios, the one exception being the mid war T-80. The T-26 and BT series had radio versions, those that had were "U" versions, eg T-26U. So for the lights you might had a radio per company or battalion or none, for the T-26/BT you could have a radio per platoon or one per company. The pre-war heavies, the T-35 and T-28 were special in that they were commanded by officers with the rest of the crew being NCOs and had priority for radios. So I would normally make a T-28 a radio equipped vehicle in ASL. Those policies continued with the wartime KV and IS series. The T-34 was like the T-26/BT with from as low as 1 radio per company to 1 per platoon to 1 per tank. By '43 the Soviets had a 2nd generation tank radio in production and was getting both radios and radio equipped tanks from lend-lease. So while there were still many radioless tanks being supplied, '43 is a useful breakpoint for the T-34.
Italians and Japanese: Both eventually tried to put radios in as many tanks as they could but production could not meet demand.
Early war radios were temperamental beasts and very short ranged for voice, usually decently ranged for Morse. German radios were better but others caught up by mid war. Platoon size matters with regard to combat efficiency. The Soviet 3 tank platoon with no radio was more effective per tank than a 5 tank German platoon if it also had no radios. From what I read about Cold War Soviet tactics, they still emphasised the platoon as the unit of fire rather than the individual tank (even though all were radio equipped), IE the 3 tank platoon fired on a single target picked out by the platoon leader rather than each tank picking its own target. Though not the peak of efficiency, it was not as bad as it first appears, speed of suppression vs number of targets serviced.
The Germans, early on, often commented on Soviet tanks bumbling about aimlessly on the battlefield. However it was not just lack of radios but under trained crews, cramped 2 man turrets, commander as gunner (RST) and insufficient and often cloudy optics all contributed to a fatal lack of situational awareness. All those disadvantages did not add up, they multiplied each other. By the end of '43 such reports did not die out but they became less and less frequent. Don't forget, the business buzzword "synergy" cuts both ways, good and bad.