Post-VMware shortlists usually come down to these two: Proxmox VE, the Debian/KVM platform with everything integrated, and XCP-ng, the Xen-based XenServer descendant managed through Xen Orchestra. Both are genuinely production-grade and genuinely free; they just embody different philosophies about how a virtualisation platform should be built. This comparison covers the architectural split (KVM-in-Linux vs Xen-plus-dom0), the very different management and support models, storage and backup stories, current pricing on both sides, and a conditions-based verdict.