They are... different. HP is staked HIVE, which is volatile. HBD is stable, or tends to be. But if one could collateralize HP and get a second-layer token pegged to HBD in return as a loan (I'm not sure if HBD directly would be possible or desirable), one doesn't have to power down and sell HIVE at bad timings price-wise to cover expenses, because they can be paid with the stable coin taken as a loan.