On the same 65 000 € gross, a worker takes home roughly 11.114 kr. more per year in Denmark than in Finland. That gap reflects the tax structure alone — before rent, healthcare, or savings behaviour come into play.
Housing is the first multiplier. Denmark has high rent pressure, while Finland has moderate rent pressure. That means part of the higher take-home in Denmark can be absorbed by rent if you land in a major city.
Healthcare and pensions go in the opposite direction. Denmark runs a universal healthcare model — Universal tax-funded healthcare; very low out-of-pocket costs. Finland uses a universal model — Public healthcare via wellbeing services counties; private add-ons exist. 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 Denmark against comprehensive welfare state in Finland, plus differences in pension capture, social safety nets, and city-level cost of living.