I'm pretty happy with XCP-ng with their XenOrchestra management interface. XenOrchestra has a free and enterprise version, but you can also compile it from source to get all the enterprise features. I'd recommend this script: https://github.com/ronivay/XenOrchestraInstallerUpdater
I'd say it's a slightly more advanced ESXi with vCenter and less confusing UI than Proxmox.