Answer 1)
If by "proper", you mean directly supported as a function of the software, then I would suggest >File >Export Appliance
This will create a file (at least as big as your virtual hard drive, plus a little more) that can be moved to another machine (or, machine
s) where it can then be IMPORTED. The benefit of this approach is it keeps all the settings, and is portable across OS', etc., as well as accommodating changing paths. The other (possibly simpler) approach is to make a copy (if going to another PC), or clone (if staying on the same PC -- VBox will give the VDI file a new UUID) and then re-creating the virtual PC settings manually, and pointing to the existing VDI instead of creating a new one.
Answer 2)
I don't think VMWare is in the repos...you would need to download and install it from outside (if I'm mistaken, I apologize...I'm sure someone will correct me). Unless you're using VMWare Workstation, it is really better for use on servers, usually in a headless environment (not that VBox can't run headless).
3?)
Better? I suppose that is more opinion than fact...it's different, with a different intent, I feel. The goal (as I see it) of VMWare Workstation is to provide a test bed, or development area, that creates compatible files with the server offerings (where they get their money). For personal, desktop use, I've found (and, it's been a long time since I've used VMWare Workstation) that VirtualBox seems to perform better (more responsive "feeling"). For server consolidation, I prefer VMWare (although work is pushing Hyper-V, now

).