Markets don't really mean anything nowadays outside the context of capitalism. It's a place you sell commodities and where there is a presumption of competition. Where does competition come from when production is not capital-driven (and then profit-driven)? The capital valorization process is still there and therefore the slew of horrors forcing humans to destroy each other so there can be 7 brands of blood diamonds.

Socialists have different perspectives on markets after there has been a socialist-won revolution. All of us know they are imbued with capitalist relations, the question is about how they might be used transitionally.

You can skip markets through nationalization, for example. A nationalized power grid operates better and more cheaply than those that operate as markets, for example. Or running a transit system. Maybe nobody needs 7 brands of bland diced tomatoes. That kind of thing.

The Soviet Union broke due to constant and merciless capitalist violence. Everything else is just responses in that constellation, like failing to sufficiently oppose that violence. A simple example is the decimation of the Soviet population by the invading fascists - the genocidal capitalists that were gladly supported by other capitalist nations so long as they thought they would destroy the Soviet Union. This hollowed out the conveyer belt of competent political actors and is why Kryschev came to power and was able to maintain it for his wing of revisionists (possibly the only time you'll hear me use that term unironically).

Co-ops would likely need more capital to survive, as they'll be less preemptively brutal towards their workers (themselves). This means lower rates of profit, requiring a larger scale of operation. Co-ops are often driven out of business by capitalist competition, where the organization of production is forcefully focused onto increasing profits by reducing what is paid for inputs: tools, materials, and labor. Co-ops are forced to operate in the same market and therefore risk going out of business when a competitor undercuts them in prices by 50%. This is one of the reasons that China forces the creation and maintenance of several worker co-ops and is careful about unions. They want those businesses to succeed and export, as China's strategy is to accept most forms of capitalist exploitation in order to draw productive capacity into its borders. They know that co-ops generally need help to survive.

If coops are more capital efficient and the proletariat definitionally doesn't own capital that means...

Some people argue that. Also we did industraial and agricultural sabotage to them. Threatened to annihilate the world and and did several wars with them. So not exactly a fair test

No, we can just wait for America to fail and let China do it.