I think that debating over the which is more efficient (small vs big) misses the point (on both sides of the argument).

We have to keep in mind that the whole marxist analysis does not revolve around what is better but on how capitalists extract value from the workforce and keep it for themselves.

In other words from a marxist perspective wage labor is another form of slavery the same way that some ancaps see the State vs the rest of society (but fail to extend the analysis to that same society)

A lot of "marxists" and/or "socialists" lose sight of this.

The way that big businesses crush small businesses is a side effect of how they take advntage of economies of scale (as an example: what happens to small shops in the US when Walmart opens a store in a small town)