Is Karpenter with Cluster API better than Cluster Autoscaler?

For a Cluster API setup, I would lean toward Cluster Autoscaler for now. The Karpenter provider comparison raises a specific limitation: it cannot calculate instance costs, so a key part of Karpenter's cost optimization is missing there.

Cluster Autoscaler doesn't handle pricing either, but it can still select a suitable machine for the workload. That makes it a reasonable choice if the Cluster API integration is your priority.

I wouldn't call the comparison settled yet. Cluster API compatibility for Karpenter has been described as experimental and still in progress, so the result may say more about the provider's current state than about Karpenter as a whole.

In an environment where Karpenter is well supported, it would be my pick. Its handling of custom instances, including GPU machines, and its cost optimization are appealing. Just don't assume those advantages carry over unchanged to the Cluster API provider.