I have skied both and own a pair of hell bents. I personally like the hell bents better, they're a little stiffer (when I say stiffer they are still pretty lose) and can get you in and out of sketchy situations better. I think the EP's are just too buttery like it feels like theres nothing to support you especially in the tip. I charge pretty hard on big pow days, pushing hard on the front of my skis and the way the hell bents lift just to the top of the snow is amazing.
If you ski K2 skis, the hell bents will ski just like them, have the same feel, turn initiation and everything will feel like the seths or fujas.
The main difference I see is that the hellbents have a more damped springy-ness to them where as the EP's are a little floppier.. Keep in mind these are the 2010's, but not much will change next year.