The practical approach
Gross salary is the amount before income tax and payroll deductions. Net salary is what remains after those deductions. For relocation decisions, both matter.
A destination with a higher gross salary can still leave less spendable income if deductions and essential costs are materially higher. Tax residency and family circumstances can also change the result.
Use gross salary for offer comparison, estimated net salary for cash-flow planning, and living costs for purchasing-power context.
Related questions
Why not just convert the salary using an exchange rate?
Exchange rates convert currencies; they do not account for taxes, housing or household spending.
Should the result be treated as exact?
No. Relocation calculations are planning estimates. Personal tax circumstances and spending choices can materially change the outcome.