I have read many analyses (here alone, let alone elsewhere) that provide well-sourced, well-reasoned arguments for both of the above positions: that British/American logistical aid was crucial to allowing the Soviets to regroup and push back the German invasion; and that the Soviet Union's reserves of manpower and resources, and relocation of industry east of the Urals gave them a wartime production capacity that Germany's relatively limited material resources and industry had no hope of overcoming.

So which one is more accurate?

(I'm trying to phrase this in a way that doesn't just ask for speculation on "what would have happened if there was no Lend-Lease?", but that's really the gist of the question.)