In terms of dollars per unit weight moved, yes. They are not only moving massive amounts of cargo with low drag, they're also relatively lightweight compared to the product being moved. Also, there's no maintenance cost to keeping a flat path across the Pacific like there is in keeping roads free of potholes.

In terms of environmental damage, not at all. Container ships burn some of the nastiest, most sulphrous and damaging forms of crude oil in existence, with little to no emissions controls.

I think rail transport is best, but I could be wrong.