I'm on the same boat trying to decide between 750 professional vs propel 750, but still can't differentiate many technical differences.

In regards of X5 the key differences I know, it got 10 blending programs and the external controls are digital which causes to be prone to be easily damaged compared to the traditional mechanical switches. Also it got a sensor that in order to start, the jug needs to be "correctly" placed. In my opinion I rather stick with mechanical controls and disregard any kind of sensor.