There is one set of circumstances in which the civilian instructor may have the edge, and that is when the student is so inept, or has a mental block at some stage in training, that he or she would have washed out of any military programme.
On two occasions I've been asked by ex-military instructors to take over students who just weren't getting it. No amount of instruction, however clear or consistent, was breaking the circle. Both students eventually went on to get their PPL(H)s. One became a very good pilot, the other gave up.
What they needed was a bit of TLC and some Zen. They felt bullied and intimidated and had developed low self-esteem.
I would say that good students benefit from a military approach, but poor students sometimes need an excess of flexibility.
And remember, a good student does not always make a good pilot, nor a poor student a bad one.