1) Both stories are based around characters whose greed ultimately brings them to grief. Mathilde's overwhelming desire to be rise above her lower-middle-class lifestyle eventually leads her to lose what she wrongly believes to be a valuable necklace. Her subsequent efforts to pay for the missing item end up plunging her and her husband into dire poverty, a worse social and economic condition than they had at the beginning.
Pahom's insatiable greed for land leads to his death. Taking advantage of what he thinks is an unbeatable bargain, he tries to get his greedy hands on as much of the Bashkirs's land as he can traverse in a single day. But the effort leaves him exhausted, so much so that he drops dead on the spot.
2) Both Mathilde and Pahom are decidedly lacking in spiritual values. Mathilde is obsessed with appearance and social status. All that matters to her is the glittering surface of life, not its hidden depths. Shallow, vain, and superficial, Mathilde has no understanding of what really matters in life.
As for Pahom, emancipation of the serfs has uprooted him from his ancestral lands, severing the deep spiritual connection that he used to have with the ground beneath his feet. Land is no longer sacred to him; it's now nothing more than a commodity to be bought and sold for profit. In the process, Pahom's peasant soul, previously so steeped in spirituality, has become corrupted.
3) Despite all the evidence to the contrary, Mathilde thinks that she has noble blood coursing through her veins. This explains why she's so anxious to be the belle of the Education Ministry Ball and why she believes herself to be better than she really is. Mathilde is utterly deluded as to her true station in life, and acting like an aristocrat when in fact she really isn't eventually causes her—and her husband—no end of trouble.
Pahom's also deeply unhappy with his relatively humble station in life. Tired of being a peasant, he wants to be a wealthy landowner, just like the aristocrats who once owned him and his ancestors during the days of serfdom. Acting like a Russian noble makes him the object of hatred and suspicion among the other villagers. It also gives him a sense of arrogance and entitlement which leads him to think that he can cheat the Bashkirs out of as much land as possible.
Both of these stories feature a protagonist who borrows from others in order to satisfy their own desire to have more than they naturally do. Mathilde Loisel borrows a necklace that looks extremely expensive in order to wear it to the ball to which her husband secured an invitation; when she misplaces the necklace, it spells the end of life as they know it. Pahom borrows seed to sow his new parcel of land, and though he is successful with it, it only fuels his desire for more and more, eventually leading to his own ruin.
Both Mme. Loisel and Pahom feel victimized, to a degree, by their relative poverty. Though they both have spouses who are satisfied with their lot—another similarity between the stories—they are unable to achieve any satisfaction. Both stories are told from a third-person limited omniscient point of view as well, making it easier for readers to understand how these two are feeling and what compels them to act they way they do.
In both "The Necklace" and "How Much Land Does a Man Need?" the viewpoint character is dissatisfied and wishes for better things in life. Mathilde Loisel would like to have a mansion, a carriage, liveried servants, distinguished guests, and a generally higher life style. She would also like to be admired.
Mathilde suffered ceaselessly, feeling herself born to enjoy all delicacies and all luxuries. She was distressed at the poverty of her dwelling, at the bareness of the walls, at the shabby chairs, the ugliness of the curtains.
Pahom wants more land. This would make him rich, because he couldn't use all the land himself and would rent it out to others. He would become a distinguished person and would be envied and admired.
The one drawback of peasant life, he declares, is that the peasant does not have enough land: “If I had plenty of land, I shouldn’t fear the Devil himself!”
That is one similarity between the two stories. Another similarity is that both protagonists get unexpected opportunities to realize their wishes. Both seem to be achieving what they had hoped for, although Mathilde's success is only temporary. Pahom has a chance to acquire a huge tract of rich land such as he has always wanted. Possibly Mathilde's one-night success might lead to better things for herself and her husband. She has been seen and admired by important members of society. There may be more invitations. Her husband might receive a promotion.
The third similarity is that both stories end in disaster. Pahom kills himself by overexertion. Mathilde loses her charm and beauty in working to pay for a fake diamond necklace. The morals of each story seem to be similar. It might be stated as: Wanting too much out of life always leads to disappointment and disillusionment. If Mathilde had not lost the necklace, it seems unlikely that she would not have wanted more opportunities to enjoy the amenities of social privilege. In this respect, she and Pahom are very similar.
Both Maupassant's and Tolstoy's stories are obviously didactic and moralistic. We identify with both of the underprivileged protagonists and feel pity for them when their hopes and dreams are shattered.