If it is for learning strapless, it is a dilemma.
The really big boards, both thicker and more area, are a lot faster to learn to ride as you can surface ride so much longer, makes an incredible difference.
On the other hand, the thinner and smaller boards tends to sit deeper in the water so you get more time and easier to waterstart.
A light mast is key, carbon foils are hugely advantageous in terms of making easy waterstarts when learning, as you got a lot more time than with heavier alu masts
A big wing which has more volume will also help in this respect.