Diff between Principal Engineer and Principal Scientist @Amazon?

Depends on the area of scientist

amzn Principal engineer is a glorified manager who has been industry too long (ie considered too old compared to peers) to be a dev and refuses to be called a manager, scope is same as sde except holier than thou attitude... TC can hit $500k and upwards depending how big of an attitude can be shown to peers Principal scientist generally works on unsolved problems like Alexa voice AI, drone flight, and cryptography, TC is usually $350k but can hit $400k if able to demonstrate same attitude as above towards peers though these people usually don't have what it takes to do that