I can’t recall 100% of this stuff as i studied it few weeks ago…still i will give it a try.
1)I think structural model says that we have only zero coupon debt in our balance sheet,which is quite unrealistic as our balance sheets also have coupon bearing debts and reduced form over comes this limitations.
2)Structural models says that Rf is constant which is again a limitation since we cannot value fixed income debt if Rf is assumed to be constant…Reduced form overcomes this limitation by assuming that Rf is stochastic.
3)Structural models ignores the impact of business cycles on credit risk…which Reduced form incorporates ie it allows credit risk to change with business cycles.