What I want to know is, where's WORKetc on this list!? It definitely compares with these. You can see why by another comparison done here: worketc.com/...
Basecamp est clairement décrite comme la référence des outils de gestion de projet. Pour preuve, Collabtive propose un "basecamp importer" et la fonctionnalité est demandée dans les forums consacrés autres solutions.
David, personnally I did not know Worketc, I guess it was the same thing for the comparison's creator, but feel free to add it and update this collaborative comparison.