Okay, let's think of the pros and cons for each ship.
Angel Loona: Classed as an Angel x Demon ship.
Pros: Loona would be more pure and take more care in herself, also have undying loyalty, would always be there for Corrupt, knowing he'll be there for her in return.
Cons: Possible war between Heaven and Hell would take place somewhere on Earth (most likely Ohio)
Death Loona: Classed as a Servant x Owner ship
Pros: Loona would end up with more respect and be acknowledged more often, automatically placing her at an Overlord status in the hierarchy given her new role.
Cons: Would have less time to spend with Corrupt with how busy she'll be collecting souls.
Classic Loona: Classed as a Peasant x Royalty ship
Pros: Loona can be taken out of her abusive zone and feel unconditional love no matter where she was, + she gets a shot at becoming royalty herself.
Cons: If Stolas is getting shit on for having public feelings for an imp, imagine how outraged everyone would be if a deadly sin of Hell was caught falling for a hellhound, the lowest of the low and the scum of the world.