RE: Question with composite
"Composites" are what the thing is made out of. "Fully Molded" describes HOW it's made. (You could make a fully composite plane without molding it, but it would be tedious.)
That really depends on what you make, and why you make it. There can be structural "advantages", but for me, the main advantage of composites, plugs and molds, is repeatability.
Let's say you have a project that's complex, either in it's shape and/or construction, or that it's a scale project, with a lot of molded-in rivets, etc..
Then, lets's say the plane gets damged beyond repair. With all the complexity mentioned above, it would be a lot more heartbreaking for me. With molds, it's still very inconvenient, but you can re-mold another identical part, or plane, in a day or two, and not have to start over with a box of balsa. These plugs and molds are a huge pain to make properly, but in theory, you only do it once.