oVirt is a very mature project, integrated with most of the Red Hat ecosystem, mostly being maintained without any new big features.

It has live-snapshot, live-storage-migration, memory overcommit management, passthrough of a very specific PCI device on a particular host, a VM portal, OpenShift IPI.

It lacks integrated container management.

OKD Virtualization is being very actively developed quickly closing gaps.
It has integrated container management, ability to leverage the k8s distributed architecture/infrastructure and to leverage k8s assets like exclusive CPU placements.
It currently lacks live-snapshot, live-storage-migration, memory overcommit management, passthrough of a very specific PCI device on a particular host, VM portal (OKD UI is more similar to Admin portal), thin-provisioning (of VMs on top of templates), hot (un)plug (disk/memory/NIC), high availability with VM leases, incremental backup, VDI features like template versions, sealing (virt-sysprep).

So OKD is not feature complete replacement for oVirt yet.