I would be more interested in leading. Would the URL be more in my favor of being accepted Vs. RL?Like sculpin said, a little googling goes a long way. But even the Wikipedia articles are a bit technical with regards the peculiarities of command.
Here's a more basic answer:
URL: warfighters. These officers are the ship drivers, pilots, SEALs, submariners who will lead sailors conducting the navy's core mission and will fight their platforms in the event of war.
RL: niche specialist communities that support various parts of Big Navy.
Staff: military versions of professions such as doctor, dentist, lawyer, supply, etc
Bottom line: do you want to join the Navy to learn to be a warfighter and lead sailors during maritime operations to include combat or do you want to be a technical specialist/profession that supports the fleet?
Edit: @JHoward beat me to it and did a decent job summing it up as well.