The SE’s have 2 things different than the regular PRX:

 

a) the pedal arms are fully machined through the entire pedal (hollow) and the pedal pads also have additional machining.  You can see this in the youtube video and the picture below. 

b) the SE comes as a package deal, you get all of the accessories for less cost than if you purchased them separately.  The accessories you get are:

 

* fully machined pedal arms

* PRX throttle tuning kit

* PRX clutch tuning kit

* PRX adjustable heel rest system

* 2 of the PRX pedal pad stops

* PRX long throttle pad

* PRX wide brake pad

A video can be found here: https://www.youtube.com/watch?v=2ymHfnVbCXA