On the same 65 000 € gross, a worker takes home roughly 11 829 zł more per year in Poland than in France. That gap reflects the tax structure alone — before rent, healthcare, or savings behaviour come into play.
Housing is the first multiplier. Poland has moderate rent pressure, while France has high rent pressure. That keeps Poland's nominal advantage closer to a real-world advantage.
Healthcare and pensions go in the opposite direction. Poland runs a public healthcare model — NFZ public system with growing private supplements. France uses a universal model — Universal healthcare with strong public reimbursement; supplementary mutuelle is common. The country with lower take-home often shifts costs that the other country leaves to your private budget.
Net-of-everything, a relocation decision should weigh strong public welfare in Poland against comprehensive welfare state in France, plus differences in pension capture, social safety nets, and city-level cost of living.