I agree. The only feature where I'd say it's weaker feature-wise is it doesn't have any form of virtual GPU acceleration - either you deal with software rendering or have to pass through a graphics card (I've done it, but it's not easy.).
Otherwise, I'd say it tends to run better than VirtualBox, though it's been years since I last used Vbox anyhow. A plus is Virt Manager comes in most distro repos, whereas VirtualBox doesn't. Also, it allows you to directly edit the XML, so you can do some cool stuff that would be really annoying (not impossible) to do in VirtualBox.
They Might Be Giants (the band)