I would argue that this is a false choice. I do not think that the issue of workplace rights is a zero-sum game in which gains by workers necessarily harm owners or vice versa. Therefore, I would choose the “side” of a good balance of rights.
It is not typically in an owner’s interests to deprive workers of all rights. Workers who have rights are typically going to be more productive than workers who do not. This is, clearly, in the interests of the person who owns the business.
It is not typically in the workers’ interests to have rights that are too extensive. Systems in which workers have too many rights end up making it hard for businesses to function. When it is hard for businesses to function, workers are actually harmed. Workers will not have jobs if businesses cannot function well.
If I had to choose one side of this, I would probably choose the workers’ side because they are typically less able to abuse the other side. Owners typically have more power. However, I still think that it is wrong to conceive of this in such starkly confrontational terms.