Obviously tanks like the Tiger were extremely powerful, but had many problems. Why didn't the Germans take a highly sucessful tank like the Panther and mass produce it to the extent of T34s, instead of using increasingly scarce resources on complicated designs?
I can't remember the title of the book which I read over the weekend because it's one of those "Wehrmacht date-date: subtitle" volumes. It doesn't describe the differences but it does describe the beginnings of German re-armament and the state of industry and the relationship between the Wehrmacht and the government in the early war. I remember enough about the Soviet Union to draw some suggestions:
Germany had an established heavy industry with traditions dating to the industrial revolution which has not been disrupted by WW1. The Soviet Union built majority of its heavy industry it used during the war in the period between both world wars - from scratch and with extensive help of American engineers and planners. This is one of the main reasons for the ability of Soviet industry to achieve volume of production. It is also why German industry was largely outdated organization-wise.
The ownership structure of German and Soviet industries - Germany had several large companies owned by politically influential families and individuals, who treated the companies as their own wealth and competed with other companies. Krupp, MAN, Henschel - those were competitors with political connections and favouritism which resembles modern-day politics. Until mid-WW2 most of those factories were only guided by general guidelines and orders much in the same way as defense industry is organized in most western countries today. The main difference between fascist and national-socialist ideology and communist/real-socialist ideology was that the former didn't try to overthrow the economic class distinction and therefore it kept ownership in position of influence. Soviet Union had all factories as state-owned and managed centrally by the government through delegated officials - there was no politically motivated competition, no issue of trade secrets, patents and rights to production other than slowly-emerging internal class of industrial managers.
German industry was not properly re-organized for wartime production during WW1 and as such during the inter-war years it followed the same methods of labour organization as in the late 1890s. This meant that unions, skilled trades, apprenticeships etc followed largely the same model which was the traditional master-apprentice relationship. In the Soviet Union the focus on mass production, as little non-political hierarchy as possible and the ability to train anyone for any job made it impossible for such relationships to thrive. Therefore mass but simple technology was preferred while in Germany the "artisanal" level of skill among workers was quite in demand.
Hitler loved the over-complicated designs. The bigger, more complex and more "kick-ass" the better. There were designs for a 175t super-heavy tank "Maus" (Mouse) and 1000t "land-cruiser" called "Ratte" (Rat) as a result of this.
NSDAP bureaucracy which was established to control the economy didn't involve itself into making it more efficient until mid-war - as it would be un-politic to assume that German engineering was not the best in the world - and never inolved itself in re-arranging ownership or control. It was satisfied with calling the shots and getting the rewards and failures or successes were understood through a political lens. The Soviet political leadership was developed along with the newly-built industry which was built to American standards (or Soviet implementations of American standards) which were arguably far superior to German ones in terms of volume of production and efficiency and it had a very clear metric of success and failure even before WW2: build as many tanks as possible.
In other words Soviet industry was geared towards simple, rugged mass production in huge quantities from the very beginning and used the expertise of qualified personnel to achieve that in the 20s and 30s. German industry already existed, being the second largest industrial base in the world after America and came with pre-existing conditions of capital, ownership, culture and workforce dating as far back as mid 19th century and was taken over by the Nazis only once re-armament started in mid 30s. Whole generations grew with German industry as a backdrop. In the Soviet Union the current generation helped build the industry from scratch.
Also a larger number of Panther tanks wouldn't save Germany from defeat. A much more important issue was lack of resources for proper mechanization of the full army - both the vehicles and the fuel - which would be necessary to properly utilize the better tanks in the first place. You can't win large-scale wars with several divisions of tanks. You need infantry to support them and control the frontlines (which needs mechanization) and then logistical trains to support both infantry and armour (which needs even more mechanization).
You are also forgetting that Soviets would build more IS-2 tanks and ISU-152 assault guns to counter them and the whole advantage resulting from better tanks would be nullified.