Population ageing increases old-age dependency and strains pension budgets. We compare Austria and Germany (PAYG-DB) with Italy and Poland (NDC), showing how design and parameters (retirement age, accrual rules, minimum benefits) shape demographic risk and redistribution. We build an open-economy CGE model with heterogeneous life courses (education, fertility, health, employment and mortality shocks), two-gender demography, and a pension-point representation that nests PAYG-DB and NDC. Using microsimulations and Bayesian melding, we calibrate each country and assess four reforms: minimum pension benefits (MinPB), progressive benefits (PPB), delayed retirement (DR), and a sustainability factor (SF). DR and SF typically strengthen growth and financial sustainability, whereas MinPB/PPB reduce inequality but may increase contribution needs; equity and sustainability therefore may diverge.