Guest integration (drag'n'drop, clipboard), USB passhthrough and audio support is also top-notch in VBox.
I haven't found a significative difference but if you have found one and can tune qemu to same level,why don't you share the xml template of your machine to the world and to upstream's virt-manager project?
> Guest integration (drag'n'drop, clipboard), USB passhthrough and audio support is also top-notch in VBox.
These things works well with libvirt too provided you are using the spice-guest-tools.
I'm mostly interested in if I can use virtualbox accelerated video with kvm because virgl3d seems well behind in that area.
I'm not even sure what your alternatives were for this before now, I guess everyone was just using samba.
Most of the VMs are encrypted, so I feel safe traveling with them. Various secrets are also encrypted, but the encryption of the VMs themselves mean that I don't have to worry about losing my device at an airport and someone else potentially getting access to things they shouldn't. There are schemes that make this work in virt-manager and KVM, but I didn't like any of them as much; I didn't want to rely on the host for filesystem-level encryption (see portability), and I have previously had a bit of trouble with full disk encryption, so I wasn't comfortable relying on that. VirtualBox essentially is also doing full disk encryption, but it's invisible to the guest and seems to be reliable.
For portability, I should be able to use https://www.vbox.me/ to install the VMs and a host onto a flash drive and be able to run any of my environments from any Windows host without additional installations. Haven't actually tried this yet (happily, I no longer have easy access to Windows machines!), but it was a big point in favor.
Most of my environments now get auto-configured through Vagrant: https://github.com/robsheldon/vagrantfiles, so I get some of the benefits of virt-manager that way.
I really don't love relying on Oracle for anything