Last time I checked the seamless mode of VMWare was VASTLY superiour to the VirtualBox one. While VirtualBox did not much more than hide your desktop-background

Last time I checked the seamless mode of VMWare was VASTLY superiour to the VirtualBox one. While VirtualBox did not much more than hide your desktop-background and make it transparent, VMware integrated the window manager of the guest OS into the host OS (i.e. guest-windows would appear in the host-OS window manager's window list). Furthermore it overlaid the screen with a button with an applications menu (native to the host-OS) sourced from the guest OS. Nowadays I am without a WMware licence, and I found that KVM and its frontends are enough for my use cases right now because I do not rely on Windows-VMs for my day-to-day work so I can always use X forwarding for an integrated experience.