The authors are coming, epistemologically, from different places. Marx is a philosopher and economist; Engels is a social and political theorist; their works are mostly grounded on very broad historical analysis. They have a very macroeconomical/ 'macrosocial'perspective. Malinowsky and Evans-Pritchard are anthropologists, who have directly and closely studied the daily lives of communities: Malinowsky the Papua New Guinea natives of Milne Bay and Evans-Pritchard the Nuer. However, a common point for all four authors is their concern with socio-economic exchanges as forming the basis of social structure.
The Communist Manifesto states that "The history of all hitherto existing society is the history of class struggles": between the proletariat (who only have work power) and the bourgeoisie (those on whom the proletariat depend upon to be employed). They argue then that the bourgeoisie exploits the proletariat through the "constant revolutionising of production [and] uninterrupted disturbance of all social conditions". The division happens because on the one hand the owners of private property thus have the power to accumulate more and more wealth, while competition amongst the proletariat creates wage-labour, which rests entirely on the competition among the workers. Therefore, as Marx argues in The Capital, the worker's labour is alienated: that is, a capitalist system artificially separates the worker's actions from his self-determination as a person.
Marxism focuses on a materialist understanding of societal development: human society starts with the organisation of economic activities: social phenomena are explained by the mode of production in any given society. Therefore, to understand the world, they start by looking at the most obvious examples of economic exchanges- like "capitalist employer- proletarian employee". For further study, you can look at how this paradigm is applied to understanding family relations and marriage in Engels' 'Origin of the Family, Private Property, and the State',particularly his argument that private property created the patriarchal gender division.
Malinowsky and Evans-Pritchard, on the other hand, were structuralist anthropologists: looking at society as a system with internal stability. Where Marx and Engels only looked at social cohesion in order to answer the question 'Why does conflict happen?' Malinowsky and Evans-Pritchard were more interested in understanding 'What keeps societies together?'; and a lot like Marx and Engels, they turned to the economic aspect; albeit in a different way. Malinowsky, for instance, looked at the economy of gifts, through studying the Kula exchanges among the Papuan natives: they were exchanging shell jewelry, not for utility and value (so they could not, by any means, be considered capital in the Marxist sense), but for enhancing one's social status and prestige. (See Marcel Mauss for how the natives very clearly distinguished between gift exchange and commodity exchange). Similarly, Evans-Pritchard looks at the importance of cattle for the Nuer society, he finds that they are not merely economic commodities/sources of food, but also a mainstay of their social interactions. (For instance, cattle can be exchanged for bride price, thus creating complex structures of kinship and social cohesion. Marx believed in an objective theory of value based on labour-power; in contrast, Malinowsky and Evans-Pritchard believed the symbolic matters.