The J-mo is significantly more burly than the FR and is not symmetrical, so obviously the FR is much easier to throw around and butter. The FR is a great park ski as it's very stable, yet has a rocker profile that gives it the feel of a softer, playful park ski. The J-mo can be a great park ski for a strong skier, and can actually handle a huge portion of your mountains off-piste terrain admirably. It's my every day ski and if I could only have one ski ever again, that'd be it as it's the only ski I've been happy with both in and out of the park on the same day.
That being said, trying out the J-mo it would certainly give you and idea as to what a rockered ski feels like and what a solid ON3P ski rides like. I have owned both skis and they are two of my favorite skis ever for their defined purposes. Before the FR I rode the Armada Pipecleaner if that helps. Huge fan of both.
Slope Style Ski Shop, Main Street Breckenridge