I encouraged him to think about his long-term career and the opportunities provided. All of the branches provide a wider variety of jobs and training than the corps. Forget about what recruiters say about job "guarantees." In the corps you're most likely to be assigned to the infrantry or driving a truck.
He chose the corp for its discipline. He learned he was right when he was sent to some training with the army. The corps was good for him, but they failed to carry out promises about college programs, so he left, even though heas offered a third tour as an MSG.
Conclusion: guess it's what he looking to do and get out of his service.
Tell him to find real soldiers and marines. Not recruiters.
Call them up and ask them to meet him and talk about their experience.
I think that would give him a better sense of the day to day.