In my experiance, solid does have a "fuller" sound. But, that said, doesn't mean laminates are not a good thing. Like also said above, some are very good quality. I am guessing the science of it is how fluid the sound waves can vibrate through any given substrate. A sound waves vibrate differently though a solid, harder sustance than it does a non solid or softer substance. It is also said that on a small instrument like a soprano uke, even a solid wood book matched back can sound different than a solid non book matched back. I guess scientifically it makes sense seeing the sound waves have to flow through two separate pieces of wood, and a layer of glue vs having no obsticles, but I have to admit, my ear would have a hard time distiquishing the difference..
Point is, I think sometimes it is way over anylalized. Unless you are some music, or sound scientists conducting a high end orchestra profesionally or something, but rather somebody that just likes to play, and your uke sounds good to you whether it be plastic, wood, laminates, or wicker, play it and enjoy it.