I couldn’t really get into StreetComplete when I tried it, but I think that’s mainly because I’m used to the iD editor’s UI and because it isn’t fully featured. Vespucci solved both of those things for me and gave me a fantastic editing experience. That said, for all I know, recommending Vespucci could leave a newcomer completely overwhelmed with options. So I would say that it’s worth starting with StreetComplete if you want a highly gamified experience for stuff like tag editing for existing objects or starting with Vespucci if you feel like you want something extremely powerful, then trying the other one if your first choice’s UI doesn’t suit you or doesn’t do what you want it to do. (StreetComplete and Vespucci are both available on F-Droid.)