On the same 60 000 € gross, a worker takes home roughly 1 231 € more per year in France than in Portugal. That gap reflects the tax structure alone — before rent, healthcare, or savings behaviour come into play.
Housing is the first multiplier. Portugal has high rent pressure, while France has high rent pressure. The two markets behave similarly, so most of the gross-to-net advantage flows straight into disposable income.
Healthcare and pensions go in the opposite direction. Portugal runs a universal healthcare model — SNS universal healthcare with low patient fees. 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 Portugal against comprehensive welfare state in France, plus differences in pension capture, social safety nets, and city-level cost of living.