On the updating page it suggests that areas of map can be specified to reduce time taken.

 

How do you find out which maps are on your machine and hence which you require to download?

Have a look for posts from @MartiniB and you will see what areas are covered by which maps. You can then decide what best suits your travels.

i definitely prefer Waze, stock maps are loaded just as backup

Discovery:
https://www.briskoda.net/forums/topic/474136-columbus-map-update-2020-mib1mib2mib2gp/

 

Amundsen:

https://www.briskoda.net/forums/topic/480367-amundsen-mib2-map-updates/