A key difference between the IRR and the MIRR is

a$.$ cash flows are assumed to be reinvested at the risk$-$free rate.

b$.$ unlike IRR, MIRR is superior to NPV as a project screener.

c$.$ IRR is a better indicator of the rate of return on the project and its reinvested cash flows.

d$.$ cash flows are assumed to be reinvested at the WACC.