Chaos Chariot vs. Gorebeast Chariot

[Vim]

I just got access to these in my chaos playthrough and I have to say I'm utterly confused. The first one to unlock is the Chaos Chariot, an all-round decent unit, though nothing to write home about, and it's upkeep is a bit on the high side.

Then you have the Gorebeast Chariot that you unlock deeper into the building chain. It costs about 33% of the upkeep cost and has higher stats in everything except Melee Defence and Speed, much like the Reiksguard and Empire Knight etc... but the Reichsguard doesn't cost 1/3 of the upkeep of the Empire Knight. I am really confused about this massive upkeep difference.

Why would anyone build a Chaos Chariot at that price?

[Vim]

I know their economy is upkeep based rather than income based, but that doesn't really explain this one part of their army being backwards. For instance, the Chosen has a higher upkeep than a Chaos Warrior even if they both have -30% upkeep costs.

This is true for every single unit chain except the chariot, where the first oen, the Chaos Chariot is a lot more expensive than the superior Gorebeast Chariot. It's just weird. Chaos Chariots are worse in pretty much every respect, and yet they cost three times as much (They both get -30% from the building chain).