Preference shares can be both equity and debt. If the shares are redeemable, then it is debt (something like a bond).If the shares are not redeemable, then the preference shares are part of the equity.
IF the preference share is irredeemable then it’s equity. If the preference shares are redeemable , then they are considered as debt and actually, the dividend paid is considered as finance cost and it’s included on the income statement.