The TriStar can carry a little more fuel (except when lim'd!), but also burns more fuel. Offload will be better, but not by much, on Voyager. Where it wins is the twin hose config with Tristar-ish offloads and decent serviceability. Freight goes downstairs. The weight penalty of a strengthened upper deck just isn't worth it if you can carry your trail spares downstairs (from the trooping/ AAR POV anyway). TriStars may cost junk metal prices but engineering them ain't cheap - not that Voyager is either. It's easy to bash the project, but let's not kid ourselves that we'd be better off with legacy types.