Opensense is often bound by single-core operations depending on where a network packet may plumb itself through the kernel. A great example is any PPPoE connections on the base OS BSD. Vyos doesn’t have these same limitations since it’s minted on Linux - which supports traffic steering.
Really though, IaC for vyos has always been rock solid. Even though the persistent config in Opnsense is cool, adding new features or configs can be a bit of a pain in the ass
I gave the example of PPPoE, the other option is to read the linked kernel docs to understand traffic steering and infer where those situations could occur.