If too slow for Raspberries, do whichever is faster, upgrade or download from scratch.
Did I manage to improve the Raspberry performance with the last release?
copying the db from the old version is definitely faster, because my Raspberry takes a long time to download the whole blockchain (maybe 1h? haven't really watched at the time precisely).
Scanning the blockchain now takes about 9 minutes on my Raspberry.
No issues at the moment with my Pi

even unlocking my account via the GUI is fast now! Thanks Jean-Luc!