This happened before my watch, but I always was rooting for Linux. Linux is winning on many aspects. Consider the featureset of iptables (CF uses loads of stuff, from "comment" to "tproxy"), bpf for metrics is a killer (ebpf_exporter), bpf for DDoS (XDP), Tcp fast open, UDP segmentation stuff, kTLS (arguably half-working). Then there is non-networking things like Docker, virtio ecosystem (vhost), seccomp, namespaces (net namespace for testing network apps is awesome). And the list goes on. Not to mention hiring is easier for Linux admins.