All brands come up with different designs and special ways to market there products..
But if talking about board design...Thats a different story
Boards can be designed to excel in specific areas to suit a riders needs.. from to beginner to advanced riders..
Etc rocker,width,length,flex, fins,concaves and shapes
Talk to other kiters or ur local kite shop

Was that nobile 666??
im going to try and demo one this week..
if so whats the pop like and how they handle chop

There are huge differences in boards that your comparing at the same length only.... what I have found

If you purely look at the end corners, if they are rounded you will be able to lean back and rotate the board & slide it ie on a wave face an it won't dig in and slow you down heaps when you push your rear foot in

if you take a skinnier board generally it will be harder to land jumps on becaue if you are landing off balance towards your toes or heels there is less of the board sideways to soften the landing.

Stiff boards are good for grip when going faster.... but can feel hard on the legs/ankles. Flexi boards you can get more pop at a slower speed and give more cushioning for the landings but tend to not be able to be ridden as fast as stiff boards as they bend like mad over the chop.

big fins obviously track the board straighter and make it more directional ( help to stop sliding out on landings ), but also add drag if too big aswell.

Concave.... helps plane at a slower speed....

Generally the best way to pick a board is to go out in the conditions you go out in normally and do the things you like to do.... then you will find some boards feel great, while others feel terrible.

Hope it helps
Nick