[graemep]

It looks like it is aimed at larger projects, whereas fossil is nice for personal projects because it was designed by and for a small team.

JJ itself uses Github, where as fossil is very easy to self-host including issue tracking, wiki etc.

[dcre]

jj is just a CLI, analogous to git alone. It doesn’t come with any of the other stuff Fossil does. I don’t think large/small project makes any difference either.