RHV is the data-center virtualization solution nearest to VMware vSphere. In the other hand, OpenStack is a cloud IaaS capable of compute, network and storage abstraction (mainly). Please do not confuse virtualization platforms with cloud platforms only because RHV and OpenStack both relies on KVM.
If your goal is to have the most tuned and stable virtualization environment and your team is going to manage it (with basic delegations to others), then RHV is what you're looking for. Instead, if you are planning to build a private cloud, with all hardware resources presented at a logical level and managed by other teams/customers, then go with OpenStack.
Please keep in mind that the more abstraction you want to achieve, the more complexity rises (software-defined networks among all others). RHV is simpler hence is consider more stable. Both environments can achieve performance, but dealing with abstraction will make it more challenging.
I suggest you to read What's the difference between cloud and virtualization?