I've paddled a few boats, I started with a Riken 2 person IK, and paddled a Force XL for almost ten years, and my wife had a Sotar for 8 years. I classify IK hulls into to styles, oval footprint and square footprint. Boats like the Force, Thrillseeker, and Sotar have an oval footprint, with curved diminishing tubes. The Lynx, Outfitter, and Tomcat are square footprint boats.
The square boats are better load haulers, and good class III boats. I don't personally like them for Class IV boating, but part of that is the rivers I run and my paddling style. I like the the Sotar boats for their durabilty, the rocker they have, and the smooth, flat seam the have where the floor meets the tubes. The square boats force you to paddle straight into big waves, if you are at a 45* angle to the wave face the bow will get forced to the side, typically causing me to get flipped. My Force could either punch those larger waves, or I could hit them at any angle and I could brace through and I wouldn't get turned. I also prefer a shorter waterline for creeks with lots of protruding rocks. (Something my Force lacked, it had no rocker) The Sotar was my favorite boat to paddle. I was 340 lbs paddling a 10 foot model, and that is about 75 lbs more than that boat should handle, but I could still go paddle my favorite local III-IV river with no problems. I'm not the type of person that says that one boat is the best, but that is a short example of my experience.