Stability constant is more for the complex:

Complex will be more stable if higher value of charge density is present.Charge density = ChargeRadiusFor stability:(i) More basic ligand, then complex will be more stable.(ii) Higher the oxidation state of central atom and higher is its coordination number.(iii) Higher the stability constant (K) CoNH363+CuNH342+Stability↓↓constant K5×10334×1011 AgNH32+AgCN2−1Stability↓↓constant (K)1.6×1071×1022