What are some alternatives?
When comparing virt-manager and QEMU, you can also consider the following products
VirtualBox - VirtualBox is a powerful x86 and AMD64/Intel64 virtualization product for enterprise as well as...
oVirt - oVirt is a virtualization management application.
VMware Workstation - VMware Workstation is a multiple operating system handler to easily evaluate the any other type of new operating systems.
Parallels - Parallels Desktop is a virtualization software for Mac users to run Windows and Linux apps on OS X.
Workstation Player - Download VMware Workstation Player for free today to run a single virtual machine on a Windows or Linux PC. Organizations use Workstation Player to deliver managed corporate desktops, while students and educators use it for learning and training.
Proxmox Virtual Environment - Proxmox VE is an open-source server virtualization platform to manage KVM virtual machines, LXC, software-defined storage and networking, HA clustering, and multiple other out-of-the-box tools on a single solution.