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The automotive stuff works better, longer, at higher temperatures. However, it is toxic and kills animals that come to lap up the sweet flavor. And it contaminates groundwater. You use this in an engine with a closed cooling loop, i.e. cooling water exchanger.
The pink rv/marine stuff is fairly non-toxic, it is designed for PICKLING ENGINES and letting them go undamaged over the winter, not so much for running it in the engine all the time. You use this in an engine with raw-water cooling, putting it in to flush out the raw water before it can freeze.
One's for use in closed-cycle engines, the other's for storage in raw water engines.