Drag and drop, when it works, it works best between desktops. Don't try it first between applications.
You can always use the Operating System networking, shared folders, called Samba in Linux.
Using access with USB devices - well, a matter of taste, but if you use several Guests it gets confusing. I also always want to have a track on the Host what I did on any of the Guests and then the direct USB device access is not good - never used it anyway.