In Ubuntu, you get the packages from Ubuntu's package repository and Snap Store. Usually the package from Snap Store is newer, but it's bundled with required library for that application. The package from package repository is older and smaller, because it's using system library. Solus basically only have one package because it's only pull the packages from Solus' package repository, and it's newer because Solus is rolling release.
Regarding privacy, Solus never harvest your data. Solus doesn't even know how many people downloading and using Solus.