Here is Sea Kayaker drag data for the 2 boats. Speed in kts, drag in lbs:
3kts 4.0kts 4.5kts 5.0kts 6.0kts
LV 1.88 3.52 5.14 8.0 14.56
Naut 2.02 3.88 5.04 7.42 13.3
So at higher speed the Aquanaut has lower drag, while at 4.5 kts and below the LV is more efficient. Having test paddled both, I am not sure how significant this is (or how accurate the calculated data). I found the LV intimidating in its lower stability, while the Aquanaut was very reassuring. They felt like completely different boats to me, but if I was in rough water it would be the Aquanaut, at least till I improve my skills.
Significance…
I have both boats.
The Nordlow FEELS much quicker. Particularly quicker to accelerate
The most common given average cruising speed in a sea kayak is 3 knots. In 4* training I’ve been told expected average cruising speed is 4 knots. Often when moving quickly along with friends my average cruising speed is 4.5 knots. For me, the 'kapp LV feels easier to move in these situations than the 'naut.
The folk paddling off Scotland found the Nordkapp LV to sprint better.
http://seakayakphoto.blogspot.com/2007/01/valley-nordkapp-lv-test.html
All that being said, the difference is not alot.
The Aquanaut is VERY confidence inspiring in lumpy water. Even experienced paddlers have noted that the Nordlow takes some attention in dimensional seas.
The Nordkapp LV is noticeably lower volume, takes less to turn and is easier to throw around.
IMHO, both are very good boats with quite different personalities.