If Plato and Xenophon were both students of Socrates who went on to write philosophical dialogues featuring Socrates, why has Plato had more staying power and influence in Western Philosophy than Xenophon has?

Part of the answer is that Plato is typically regarded as a better philosopher than Xenophon, and his dialogues aren't only (or even primarily) read as a historical account of Socrates; they're read because they're independently philosophically interesting. While Plato's dialogues feature Socrates, and at least some of the views are believed to come from Socrates, many of these dialogues (especially later ones) are believed to express Plato's own views, albeit by using Socrates as a mouthpiece. Exactly where to draw this line – i.e. deciding how much comes from Socrates and how much comes from Plato – is a matter of scholarly dispute. Xenophon is actually one of the sources consulted in trying to answer this question.

Here's a relevant quote from the Stanford Encyclopedia of Philosophy (a standard source in academic philosophy):

We may read Plato's Socratic dialogues because we are (as Plato evidently wanted us to be) interested in who Socrates was and what he stood for, but even if we have little or no desire to learn about the historical Socrates, we will want to read Plato because in doing so we are encountering an author of the greatest philosophical significance. No doubt he in some way borrowed in important ways from Socrates, though it is not easy to say where to draw the line between him and his teacher (more about this below in section 12). But it is widely agreed among scholars that Plato is not a mere transcriber of the words of Socrates (any more than Xenophon or the other authors of Socratic discourses). His use of a figure called “Socrates” in so many of his dialogues should not be taken to mean that Plato is merely preserving for a reading public the lessons he learned from his teacher.

This is actually from the entry on Plato - more here: https://plato.stanford.edu/entries/plato/#Soc