most profitable run I'vefound is
NB-Honshu-Malta-NB and again:)a.k.a cobalt-engine parts-cardamine
yes it is smugling but I can earn with 3000 cargo prison liner same money in almost same time as adv.train with 5000 cargo space on diamond-niobium run. Since I am in RP slaver I use this run only when I need a lot of money quickly as is posible ... normaly I do Huston-Malta and back which give me fair profit in fair time but it is less than previous run.