Yeah I see Perkeep as being a little bit more aimed at the personal archiving problem, especially around larger files such as photos and videos. It feels a bit like an open source equivalent of Dropbox in that regard. Dogsheep is much more aimed at smaller, highly structured data which you want to run arbitrary queries against, hence the focus on SQLite. I think the two projects could complement each other - having Perkeep archive my personal SQLite database files seems particularly appropriate for example.