Cost of manufacture and the use of scarce resources has to figure prominently in mediuum tank design. Also mobility in difficult or ice ridden terrain .
The Sherman cost about 2/3 that of a MkIV in dollar terms to produce, and less than half that of a MkV. Dont know the dollr cost of a T-34, but it was easy to make, much easier than the equivalent german models. However, German tanks held a distinct technological advantage in the gun-armour stakes.
All tank design, and production is a compromise between engine power, gun power, and protection. Slight adjuncts to that are the cost of the technology, and overall production costs. Finally there may sometimes be issues of reliability, and commonality (ie haviong too many differnt marks and models, makes the logistics issue a real nightmare)
Now, firstly to break down by nationality (marked 1-10, 10 being perfect, 1 being abysmal)
Germany:
Engine/Mobility: 7
Gun Power: 9
Protection: 8
Technology Cost:6
Production Cost: 3
Reliability: 5
Commonality: 3
Total score for german tanks: 41
Best tank in German lineup: Panther
Germany loses out badly in the technology costs (her face hardened armour, engine and gun decvelopment costs, and her pioneer work oin the AFV sphere all made for added expense). I believe she had some issues with reliability (particulalry with the panther, and the overall lavish fitouts and standards of finish all worked against them when it came to numbers
US
Engine/Mobility: 6
Gun Power: 5
Protection: 3
Technology Cost:5
Production Cost: 8
Reliability: 6
Commonality: 8
Total Score: 41
Best US Medium: M4 Sherman
The US scores badly in the firepower and protection stkes. Their tanks were adequately mobile (although overall i think they were slightly worse than Germany). Because the US was coming from so far behind (take a look at their M2 type if you dont believe me), they had to invest a lost in the technology to bring their tanks up to speed. The US scores top marks in production costs, and commonality, and I consider them to be reasonable in terms of relaibility
Britain
Engine/Mobility: 5
Gun Power: 4 (have not included 17 pdr in Medium tanks)
Protection: 5
Technology Cost:5
Production Cost: 5
Reliability: 6
Commonality: 4
Total : 34
The best wartime medium in the british inventory would be either the Churchill or the Comet IMO
British tank development suffered a lot of problems in the war. The separation of cavalry roles and Infantry support roles stunted and deformed British tank development. Armament, in the early stages with the two pounder, which was unable to counter German 88s effectively, cost many tanks, many battles and a lot of tankers lives. British engine development was backward at the beginning of the war. The Commet suffered from a relatively weak armament at the end of the war. However, British technoilogy costs were still better than the germans, and the production costs of their relatively simple AFVs also quite good.
IMO the best Brit tank, though a close competition, is the Comet.
USSR
Engine/Mobility: 7
Gun Power: 6
Protection: 6
Technology Cost:7
Production Cost: 6
Reliability: 6
Commonality: 5
Total 43
The Soviets are not clear winners in any single category, however in every category they score quite well. This is because in my opinion, Soviet tanks are a good balance between all of the various factors. Looking at the t-34, it was mobile because of itrs wide tracks, it was well armoured, because of its sloped armour scheme, it had adequte gun performance, its technology was relatively easy to develop, because it was an evolutionary rather than a revolutionary development. It was simple and easy to build, And the Soviets were succesful in the commonality area IMO
Best Overall tank IMO is probably the T-34, although ther heavier armouring scheme of the KV-1/2 make it tempting
France
Engine/Mobility: 3
Gun Power: 6
Protection: 7
Technology Cost:5
Production Cost: 4
Reliability: 4
Commonality: 2
Total: 31
Best wartime tank: Somua
Italy
Engine/Mobility: 2
Gun Power: 4
Protection: 3
Technology Cost:4
Production Cost: 4
Reliability: 3
Commonality: 4
Total 24
Best overall. Not a tank, but inmy opinion the best Italian tanks were their varios Semoventes
Japan
Engine/Mobility: 4
Gun Power: 4
Protection: 4
Technology Cost: 2
Production Cost: 3
Reliability: 4
Commonality: 2
Total: 23
Best overall
Shinhoto Chi Ni
The best overall medium tank, on the absis of theabove assessment, therefore gets down to either the T-34, or the M4, taking into account the non-battle related variables. My instinct tells me that the fonal top position should go to the T-34, but this might be a matter of opinion