The primary different between how pod<>pod communication occurs in K8s is that it's (by default) achieved through IPVS, rather than netfliter/iptables (this wasn't the case until 1.9). In any case, I don't know if there are significant performance advantages with IPVS, it was adopted because it scales effectively past several thousand hosts.
The advantage to using Kubernetes though is that you have the option of going with adopting commercial network drivers that have the full weight of the cloud-native ecosystem driving the development behind them.
This scratches the surface, but if you're looking for maximum throughput and performance, you're probably going to have to go with something other than what comes out-of-the-box.
_kc