Writing skill consists of three virtues: Clarity, Concision, and Euphony. In legal brief writing, most writers would rank the virtues in that order. But clarity is paramount in legal writing not primarily as a writing skill. Broad clarity depends primarily on what you say rather than how you say it, and achieving broad clarity depends most on knowing the law, learning the research, and formulating precise arguments. This broad, foundational clarity is defeated by the predominant writing method in law, assembling scraps of information. Better writing won't save the brief drafted by these flawed compositional methods.
This equivocation about clarity's scope allows panaceaists to oversell Clarity. Once you separate clarity in conceptualization from pure writing Clarity, it is not chairman of the writing virtues. The honor of centrality belongs to Concision. First, Concision is most aligned with the basic function of writing. A given written work is first and foremost an act of information compression, as rarely do we communicate propositions lacking alternative means of transmission or discovery. The goal is to convey as much as is relevant as efficiently as possible. Second, Clarity is overvalued not only because of the confusion about its source but also because of the marketability of its pedagogy. Using many words, most anyone can make an idea clear, provided he understands it. Concision and Clarity both cooperate and conflict because you achieve Concision by eliminating the obvious — that which, if included, would only marginally clarify. Efforts focused on Clarity render still worse a verbose work, too boring to read.