3 strand is what it calls for. I don't think the hardness of the lay will be that big of a factor. When the wheel starts squeezing the twist rope, the lay will be automatically tightened until it matches the force of the load. The final breaking strength might be greater for the soft lay as less tension is exerted off-axis on each of the fibers. But that is purely speculation on my part.
Chances are good that you can't get to the breaking strength of your rope with the Maasdam. It is only good for about 1 ton, then you will run out of leverage and friction on the wheel.
There will be more rolling friction and stretch using the softer lay rope.