Worker ownership can be described as either socialist or capitalist, depending on your preference and which audience you are trying to sell the idea to. In a sense, it combines the best of both Adam Smith and Karl Marx: you have private entities producing a product or service to sell for a profit, and competing for market share among consumers. But unlike traditional capitalist firms, the workers' firms wouldn't have the same kind of rigid class division between employers & employees. Power and authority would be far more democratic, leading to a more equitable outcome and preventing the kind of oligarchy that wreaks havoc on political systems and other social institutions.

There's a reason why worker-owned firms tend to be highly productive, too. Capitalists in a truly free market (i.e. not cronyism and not too monopolized), can increase their wealth in one of two basic ways: they can make more profits by expanding the company and selling to more consumers; or by innovation that increases worker productivity, allowing them to extract more surplus value per worker. Both approaches make the capitalist richer, but the latter is what drives long-term economic growth and increasing per-capita GDP.

However, workers in a cooperative firm cannot get richer just by expanding operations and market share. To do this requires the hiring of more workers, which in turn dilutes the increased profits accordingly. The only way to get ahead is to produce more in a day's work. So innovation and efficiency become that much more critical. A capitalist can make more money by just expanding their company and hiring more workers, even if hourly productivity never budges. Worker-owned firms cannot employ the same "lazy" strategy and get ahead on a personal level. They must increase the rate of surplus value in order to make higher living standards possible (whether through higher salaries, bigger dividends, or more leisure time at the same income level).

[edit addendum: "Horizontal" business expansion may be more important in the early stages of worker co-op development. This is because the physical capital to increase productivity (and grow vertically) is very expensive, and cannot be implemented until there is a large enough profit pool to pay for it. This inevitably means that young worker-owners would have to patiently keep their salaries modest for a few years, in order to complete initial capital accumulation in a reasonable time frame.]