I'd say that it depends on the kid's preferences more than anything else.
Our DS, with a new LEGO kit, will follow the included directions to build the object. He's reasonably good at doing this, but I'd say it's not his favorite part, as he generally isn't attached to keeping the pieces together once it's finished.
In fact, he seems to prefer taking them apart afterwards and putting them together in new ways for his own creations (often with stunning detail). We converted his old train table into a LEGO table where he has hundreds of pieces scattered about on it, all from various kits we've acquired over the years.
