What other option do you have if you want to support developers across Linux/Mac/Windows?

VMWare player? Besides it not being OSS, I didn't notice any performance benefit.

The bottleneck (for my web development needs), is around the spottiness of shared folders and JS tooling that needs to keep a watch for file changes.

If you're using vagrant to manage the VM and either use widely-supported or self built base boxes, each developer can use whichever works best on their platform.

So you might have a windows dev using hyperv, another usimg vmware workstation, a mac user with parallels, a linux user with lxc and another with kvm.

Parallels always took that crown in my book, though I don't have that much experience with VirtualBox.