Why do we have something far better under grace than under the law?
Under grace we have something far better because the law, though holy and perfect, had no power to help mortal man keep it. Grace supplies the Holy Spirit's power, enabling the righteousness of the law to be fulfilled in Grace Age believers, which the flesh could never accomplish under law.
Les explains that the law was perfect and holy, but it had no power within itself to help the law keeper keep it. Man without the Holy Spirit, in his own flesh, could not begin to keep that perfect law, so it became weak, beggarly, and a yoke Israel chafed under constantly. Under grace, however, we have something far better. Les points to Hebrews, where Paul lays out that which was good under the law but is far better under grace. In Romans, the righteousness of the law, perfect from God's point of view, can now be fulfilled in us as Grace Age believers because of the power of the Holy Spirit.