Federal versus State
Generally speaking, clerking with a federal judge will be considered more prestigious than clerking with a state court judge. As such, students at the top law schools are competing more aggressively for federal clerkships than for state judicial clerkships. Given the prestige of a federal clerkship, it can often make you marketable far beyond the geographic area where you are clerking.
See Will a Clerkship Enhance My Marketability? for more information.
The “ranking” does not stop at federal versus state, though. Within both federal and state courts, there is a hierarchy of stature at play. At the federal level, the order of prestige of clerkships is typically 1) the Supreme Court, 2) circuit (appellate) clerkships, 3) federal district court (trial court) clerkships, and 4) clerkships with United States magistrates (who do a great deal of the legwork for federal district court judges). There are also several specialized courts (such as Federal Tax Court) that are of approximately the same prestige level as federal district court clerkships. For obvious reasons, clerking for the Chief Justice of the United States Supreme Court is generally considered the most prestigious clerkship possible. And, similarly, because there are many more people competing for clerkships in larger metropolitan areas, a clerkship with a federal district judge in the Eastern District of New York is more prestigious than a clerkship with a federal district judge in a small town in the Midwest, for example. It follows naturally, then, that attorneys who clerk for the most prestigious judges are typically those for whom clerking increases marketability.
See What Skills Do You Learn in Judicial Clerkships that Help You in Private Practice for more information.