On the same 65.000 € gross, a worker takes home roughly 2 766 € more per year in France than in Germany. That gap reflects the tax structure alone — before rent, healthcare, or savings behaviour come into play.
Housing is the first multiplier. Germany has moderate rent pressure, while France has high rent pressure. That keeps France's nominal advantage closer to a real-world advantage.
Healthcare and pensions go in the opposite direction. Germany runs a public healthcare model — Statutory health insurance (~14.6% split with employer) gives full coverage. 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 comprehensive welfare state in Germany against comprehensive welfare state in France, plus differences in pension capture, social safety nets, and city-level cost of living.