Originally Posted by Archived Post

They're both ion engines, just two different designs and operating principles.

The Standard Gen/ Next-Gen ion engines are designed for lower longer burns achieving faster speeds at lower acceleration. uses electrodes and multiple moving parts and needs more maintenance. A potentially huge benefit is a standard ion engine produces an electrical charge as a byproduct that could be harnessed and feed into the power system.

The Vasimr Ion engine uses electromagnetic field instead of electrodes, has very few and smaller moving parts that require less maintenance. The Vasimr engine also provides a larger thrust over a short amount of time, however in doing so in produces a huge amount of heat that needs to be properly dissipated. The strong electromagnetic fields needed for the engines also produces hazardous dangers for electronic devices on board and requires a much greater amount of energy.