If a pipeline bursts, somewhere along the line will be a shutoff valve. Most tank barges are divided into separate inner tanks, not sure about ships but I suspect it to be similar, especially for balancing weight, but I only have experience working with barges. If one of those tanks ruptures, the whole tank spills. More than one can rupture, like if there is a collision.

Take the Miss Susan and the Summer Wind for example. Miss Susan was coming out of Texas City strung out (barges in single file line) in the fog to head eastbound on the canal. The Summer Wind was inbound on the ship channel. Poor communication and visibility made them scrape some paint. Nothing could be done, the barge spilled 4000 barrels, no shutoff valve. (1 barrel = 42 gallons)

When pipelines go under a body of water, they'll have relief valves on either side. A sudden change in pressure will kill the flow. Of course, some will have to spill for them to be activated, but it can be cut off much quicker.

Billions of barrels of chemicals move every day without incident, but if there is gonna be an accident I'd much rather it be a pipeline than a ship or barge.