Rigid
Drop-stitch technology allows you to inflate to high pressure (up to 6 PSI) while maintaining the shape of the chamber. Think of how rigid inflatable standup paddle boards need to be to have a person standing with all their weight in one spot - it's the same technology.
You can see from this image that the high pressure DS floor creates a kayak hull with corners (called chines). The chines make the kayak track straighter.
The high pressure floor spreads the weight of the paddler more evenly, so the hull is flatter and glides better through the water.