Answer:
Either you or Miguel is leading the group.
Step-by-step explanation:
When using compound conjunctions - either... or and neither... nor - we tend to feel like using a plural verb, which may be incorrect. Most of the time, the right way to conjugate a verb in sentences with compound conjunctions is in the singular.
Something else that can be confusing in the sentence we are analyzing here is the fact that "either" is followed by "you". As we know, the right verb form for "you" is "are". However, even in this case, we should go with the form "is" because "Miguel" is the closest noun to the verb. Therefore, the correct answer is:
Either you or Miguel is leading the group.