Debt is generally cheaper because lenders face lower risk. Because debtors hold priority claims on assets during liquidation and receive guaranteed fixed payments, they demand lower returns. In contrast, equity investors require higher returns for taking on higher risks.
Companies also often prefer debt because it doesn't dilute shareholders which issuing new shares would do.
It is funny that usury is so evil in Islam at the same time Islam very clearly allows men to own and rape female slaves, "those whom your right hands possess" (ma malakat aymanukum).
Those slaves being raped must be so comforted by knowing that Islam forbids cash loans at reasonable interest rates.
Different mechanics, but stripping everything away, roughly the same.