I've observed that eminent thinkers are generally adept at using words to communicate their thoughts. I've also observed that renowned literary writers usually manifest a philosophical bent of mind in their writing. It appears to me, then, that philosophers and littérateurs have quite a bit in common inasmuch as they both draw on the combination of two key competencies: the power of ideation and command over language, in order to be successful. However, having pondered over this briefly, I see that there is at least one fundamental difference between those who are primarily thinkers and those who are primarily writers.
To philosophers, whose modus operandi typically involves engaging in discourse with other thinkers, language serves as a useful tool to explore ideas and examine concepts. To littérateurs, whose focus typically is on developing narrative that would engage readers, ideas and concepts serve as basic props that, when enriched by the embellishments of language, could tell a compelling story. The quintessential thinker is seized with the quest for sagacity in the process of contemplation, whereas the quintessential writer agonizes over the search for precision in the process of articulation.
Philosophers delight in clarity of understanding, littérateurs in artistry of expression.