Some models turn out better than others
Another reads and more or less follows the instructions, but skips some difficult steps. The end product is noticeably better, but still not all there. It looks more like the picture than the first child’s product, and is able to do more, but the skipped steps prevent it from being all it was designed to be.
Some lives are more fruitful than others
Some folks don’t spend much time in God’s word. They basically wing it. Through the gifts of the Spirit, their lives do indeed resemble Jesus’, but in a rough kind of way. They are missing some things, other parts of their lives don’t quite line up, and they don't do nearly as much as God made them capable of doing.