I kinda feel bad about the fact that I appreciate more the father-son bond between Hordak and Imp compared to Gyro and Boyd.
While I still believe there are plenty of nice parallels between both families there's something that drags me more towards my alien boys. Something about their bond feels deeper to me and if there's something that I truly appreciate from SPOP is their approach on show, don't tell, especially when it comes to Hordak.
Hordak and Gyro created their child with science, Imp being a cloning experiment and Boyd being an android, but Imp feels more personal because he shares DNA with Hordak and he's his only creator, while Boyd was a collaborative work between Gyro and Dr. Akita.
Judging the characters on their own:
I find Hordak more interesting than Gyro due the complexity of his character. Yes, Gyro is also complex but unlike Hordak he wasn't born doomed. It's enough to compare their abusers to find out that Horde Prime is worse than Dr. Akita, also Hordak is physically disabled and his technology is not enough to compensate for his body, which adds to the many challenges he has to face.
Boyd is more interesting than Imp because he's fully sentient and possesses a high intelligence, plus he has his own background story which not only depends on Gyro. Meanwhile, Imp is a simpler living form, capable of learning but unable to speak with a voice of his own (he can record other people's voices and play them at will, but we lack further knowledge about how this works), and outside of Hordak, Imp doesn't have a purpose.
Gyro and Boyd's story is the one of a father and a son who had a close bond until Dr. Akita used them to fulfill his selfish desires, leaving their relationship in bad terms and separated for years. It's when they reunite to face their abuser that their relationship is finally able to heal. The story is ambiguous about their current status (is Gyro co-parenting with the Drake family?), but the message is clear: everything will be better.
Hordak and Imp's story is not tragic, we are only shown how their regular interactions go. Even when there's no plot, they actually care about each other. Hordak was indoctrinated to only feel appreciation and devotion towards Horde Prime, so to see him displaying physical affection for someone else is surprising. Imp serves as Hordak's spy and since they keep such a close relationship, Imp is the only one who knows Hordak's secrets (such as his illness) and acts with loyalty towards him. Once again we have an ambiguous status, as Imp was left behind when Horde Prime took Hordak away. All we know is that ex-members of The Horde took care of Imp, but it's unclear if they reunited again after the war.
I guess my preference relies on the fact that Hordak and Imp have an established cute dynamic from the very beginning and their split was not something they chose. Imp was not created on purpose, but Hordak fully embraced him, maybe because he seems in Imp the same that he sees on himself: a failure. He could have given Imp the same treatment he received from Prime, but instead he acted like a dad for him, and for that he won the title of "Hordad".
I'm not saying Gyro and Boyd are less important, but we were left thirsty for more interactions between them.
Anyway, for your consideration, cute Hordak and Imp moments.
Casual petting in the middle of an evil speech.
Imp kicking Hordak for not showing enough gratitude to Entrapta.
Imp teasing Hordak because he knows he's not over his crush on Entrapta.
Posing with his dad before destroying the kingdom of Salineas together.
He knows he's a spoiled baby.