Russian Aircraft and low load

‎Hi to every one

There is a big question that I ask to my self but with no answer .

Why the russian combat aircraft has low external load than the westrn aircraft in the same class . Can any one answer me and if we look to the Mig-29 we see the first class Mig-29A (9.12) has extrenal load up to 2000 kg and in the mig-29S have 3000 with no difference in the power and in the mig-29SM and SMT had increase to 4000 and 4500 with no any difference in power (engin threat) why the first A com with low load and the others had increase with no difference so why thy did it from the first, and why low load ? . if the answer is the design of the wing and its area or the russian load point its capacity very low .the same question for SU-27 and it’s family compared with F-15C and E in this case we see the SU-27 and it’s family has power above the power of F-15 . Can I hear a convinced answer ??? .