Which kind of board is easiest to work with?
Pine.

It is the the only one of the choices (other than plywood) that will give a natural wood finish easily. Also its edges do not need special treatment, unlike plywood. While veneer makes all of the other choices feasible for finish, that is a complex process on a multifaceted model. Every face and visible edge needs to be precisely laminated.

Pine is the softest, can be easily cut and drilled, and glues well. I cannot speak to laser cutting. 

Pine is more easily deformed, but a model is not likely prone to much stress. Shrinkage and swelling might be a bit more of an issue, but less so if well sealed.

A slightly more forgiving wood is poplar. It is a bit more stable and tends to be clear (knot free). It is also a bit more expensive, but not prohibitive.