It depends on the apps we want to have when talking about implementing these by Jolla or external developers. All things related to Nextcloud for example would benefit from the already system wide implemented Nextcloud account data, so in this case it would be better if Jolla does the job. Especially syncing Notes, Tasks (we still need a tasks app in general on Sailfish!) would be such sync, perhaps even documents, and implementing Talk into Messages or Phone App would be very cool. Phone Track would also be nice.
But other apps not related to already implemented system features (like accounts) may be better in the hands of independent Dec’s.
Nevertheless I would be willing to pay some money for features I want - as well to independent devs as also to Jolla itself (hey Jolla Team, what about a better camera app and support for better devices like Xperia 5 and 1 (or better their II-Version when these will join Sony’s open device program)?