Always difficult to know which way to go on something like this. I'd suggest that if the interviewer expects you to know it all, which will undoubtedly become clear from the in-depth questions, the chances are pretty good that they're looking for an excuse to fail you. Conversely, if you
DO know it all, there's still a good chance that they'll flunk you only, in this instance, it'll be for being too theoretical and, by implication, not practical enough.
I'd be giving the practical answer that's short on detail but long enough that the interviewer sees that you know the difference between a VOR, a NDB and a Localiser. That way, you put the ball back in their court to ask a more in-depth question. They obviously have a right to expect that you'll know a fair bit about it, because they'll know what's in the training syllabus - probably better than you know it.
As a purely personal observation, I'd be thinking that if they want more detail than is practically useful, they may not be the sort of mob I'd want to work for. It
IS a case of "horses for courses" though, because it largely depends on the type of job you're being interviewed for. The standard, garden variety flying job (airline or GA) shouldn't require you to demonstrate a thorough knowledge of it but, if it's an instructing type of job, all topics are fair game... and in fairly significant depth.
That's my tuppence worth, anyway...
