Great discussion there, guys, I just want to make a point about Stalingrad.

When the german advance seemed unstoppable, the russian high command was adamant about not allowing the enemy past the volga, so Stalin sent sapper armies (the SU was the only country in the world to have a sapper ARMY as opposed to brigades...) to fortify the city. Once the germans finally took control of the city with great loss due to the massive fortifications and fierce resistance, and dug in themselves, the red army kept stupidly (Zhukov style) storming the fortifications over and over. Hence the huge casualties. A city fortified by the russians and then the germans should have never been assaulted in the first place, but the russians were too serious about the whole "not a step back" thing...

I also want to agree that german tanks were a lot more sophisticated than allied and russian tanks, and were production-heavy. But this is also due to their role as speaheads. They were not intended to form the bulk of a battle line.