This question gets asked a lot, and it really depends on each person, their character, where they surf, and the skill level they have. Our view is that a Adult softboard like the Numfish Rush Softboard is the best choice. Lets outline a 3 common scenarios to help you understand why we believe that to be the case, from the perspective a learner who is not yet familiar with handling a surfboard.
You accidently hit a corner of a doorway/Car door/shed door/fence/gate with you board. If it was a hardboard then sharp edges and repair work is likely to be needed but if it was a softboard it is likely still to be usable and safe but scarred.
Walking back to the car after a surf and the wind catches the board and it flies out of your hands smashing into the pathway. If it was a hardboard then multiple dings and sharp edges and repair work will be most likely required but if it was a softboard it probably still usable and safe but maybe with a few scuffs.
While riding in the surf the board flings out and hits a young child in the face in the surf. If it was a hardboard then it most probable the child has a large open wound that will be best taken care of at a hospital, but if it was a softboard the child will likely be sore, bruised and a bit upset.
Its pretty simple to see why so many people use adult softboards to learn to surf based just of these 3 example scenarios, its all about keeping the whole experience fun, carefree and as safe as possible for everyone .