I would have thought that they would be incremental updates, and hence small, rather than a complete map install, which would be large (the full install of the European maps for my zumo 500 is well over 2GB and won't fit on the zumo, so the UK and Ireland sections have to go on a 2GB SD card).
The updates should contain all the latest road changes (re-naming of streets, new roads, one-way systems, and other updates and corrections). Whether you need them all is debatable. Perhaps a quick email to Garmin/Navigon support would confirm or refute this? I couldn't spot anything obvious on the FAQ section of Maps & More.
Nick