not sure I should call him Nicks little brother but that's the one. The hull shape may not be the epitome of fourpanels in s&g, I'd like the bow to be a little easier to turn and some forming bulkheads to facilliate the construction where the deck panels meet near the bow/stern. But from a handling standpoint, cockpit ergonomics and efficiency of design it's a quantum level beyond the NBxl on each of those attributes.
Handling-the Merganser turns from the middle where the motor is,,the NBxl pivots from a point about a foot further forward. Weathercocking-the NBxl is almost uncontrollable in high winds, the Merganser sits deeper in the water and responds to a lean with the line taken being a big one(it tracks well)but the fact is that it turns,,the NBxl stern will slide out in high winds, it'll turn quicker but with less controll as the wind hits the stern and the bow digs. In waves the NBxl bow will be stuck more whereas the Merganser will have it's control edges/panels closer to the paddler where it's greater rocker sits you lower in the water. So although the Merganser looks like it's got a low volume bow it's got the paddler sitting lower in the water so the net effect is that the paddlers mass can control that sharp bow more easily. Oh,,efficiency,,the wetted area of the NBxl is more than needed. It's another big volume cruiser like the Chesapeake.

Cockpit ergonomics,,I bet the NBxl is actually a higher volume hull but the footroom/legroom and ease of exit/entry in the Merganser is much greater. The keyhole coamings on the NBxl are nonsensical in a short coaming. The use of a coaming recess on the Merganser integrates a downward sloping thigh brace that requires only flat minicell to pad out compared to upward sloping thigh bracing in the NBxl that is simply the shape of the underside of the cambered deck. In other words the recess separates out the requirements for thigh bracing from the design of the deck enabling a deck with lots of foot room, adequate lower aft coaming and the front of the coaming is somewhat protected because it's closer to the peak of the fordeck. Which may seem like a little thing but it reduces the chipping that can occur on a coaming when the kayak is rolled on it's deck.

Efficiency of design-4mm okoume and one 1/2" coaming spacer is all that is involved in the construction. The NBxl has 3/4" sheerclamps, under deck carlins, 4,6,9mm plywood. The Merganser can come out lighter, more durable, and use fewer materials and epoxy.

that's just for beginners. If you're building from plans Vaclavs Cirrus I'm guessing might have a less twitchy handling hull,,but that's guessing. Once we get Dave Murray in Jamul to build and paddle a Merganser it'll be a guessing game,,,as best I can tell Dave Murray has built and PADDLED enough s&g designs to be the resident kayak kit consumer expert around here.