7z definitely gives the best compression sizes, and as you say, makes a whole set smaller to download, which can only be good. Bit annoying when needing to download a whole set again though, but definitely worth it for those managing such a project.

I haven't updated my NDS set with the 2 newer update torrents yet. I currently just have the main 115GB No-Intro set, but I suppose I should to bring it up to date.