Firstly, I rarely say this but you should do a search, lots and lots of threads with lots of info on these skis.
I will also answer you to the extent I can,
I've ridden 3 (not the Chopstick). From what I've heard, chopsticks are much less rockered, fairly stiff, heavy and not all that popular with most people
Hellbents are pretty soft, although more solid than the EP, obviously float amazing and come in a range of sizes. You can charge relatively hard on these, although they will wheelie out on drops. Downside is that I didn't like them on hardpack, without early taper they are pretty unpredictable. I didn't like the varying length of effective edge resulting from this. They are also the heaviest of the 3, being light, I didn't like this.
The JJ I only had a few runs on and only one pow run. For what its worth, they were good on hardpack (best of the three) and fairly light. Held up the best at speed too. However they float less well, and are less surfy than the other two. This is due to having less rocker and to being a significantly narrower ski (1.5 cm narrower throughout) They have narrow edges so may get broken up in the park and because of the shape centre mounting isn't advised (don't know if that matters to you).
The EP Pro is the softest and the best in pure pow. In my opinion its also the most fun. I thought they were better on groomed than the Hellbent (due to early taper). They are by far the 'surfiest' and float the best, and for tricks in to pow they are hard to beat, until you land wrong. The soft flex means get it wrong of something big and wheelie time. It also makes charging not ideal and crud less than fun. I skied these all last season and loved them but I sold them just recently. I'll be riding 189 Surface One Lifes this season.
Pow/Groomed/Drops/Bit of Jibbing = JJ
More Jibbing/Bigger Drops/Pow = Hellbent
Jibbing around/Deep Pow/FunFunFun = EP Pro
ON3P Caylor, Surface New Life and Atomic Bentchetler are also worth looking at. I haven't ridden them but: Bentchetler is like a wider JJ, and the New Life is a more rockered, lighter chopstick. ON3P Caylors are meant to be sick too, someone else can tell you better about them.