Focusing on Soviet November 42 counterattack:
The worst loss was the trained German men lost in the pocket, new equipment can be produced (and equipment goes obsolete by itself after a while i.e. all those 37mm PAKs). Thats why a breakout should have been ordered as soon as possible.
Initiative was lost already (you can argue it was lost when Typhoon was defeated in December 1941) and would have been lost in 1942 regardless of what the Germans did strategy wise.
Land was kind of important, taking away more agricultural areas hurt the Soviets in 1942 (there was some famine), by November 1942 the Germans had taken and ruined these areas so the land was less important to hold in November 1942.
Time, not really by that point, Smolensk 41, Kiev 41 and such you can argue about lost time, maybe even some of the July 42 decisions were about lost time, but by November 1942 the initiative had been lost.
Politically the loss of the Italian army really hurt Mussolini politically, perhaps more than anything else.
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The best case scenerio is Germany gets most of the soldiers out of the pocket, beats Mars as in OTL, without a convicing victory, the Germans negotiate a peace somewhere between the 1939 and 1941 boundries
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Medium case scenerio, the Germans are only partially sucessfull getting out of the the pocket (sort of a Falaise pocket scenerio)
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Worst case, the breakout is botched, Stalingrad falls early, Army group A is cut off as well, war ends early.