So far, the trains are ahead in developing new capacity, and are more versatile--at least for the time being. The rail loading facilities were built because the pipelines were not. When light sweet crude is selling for a $30 discount because there is no way to move it (as it was), someone will find a way, not only to move the material, but to profit from it. They did.
The other simple advantage is that the EPA hasn't been able to ban trains yet.
It costs about $5/bll to ship by pipeline vs $10-$15/bll by rail car. (Railcar cost = up to 3 x pipeline cost) Oil sources, where infrastructure is insufficient, might use rail car, ...but generally the best buy is to ship to a terminal nearby, then continue the shipment by pipeline.