As I understand it, the difference is a certification issue related to output power of the beacon and its rated reception distance. The common, garden-variety NDB has greater range and is used for enroute track guidance as well as instrument approach. In the case of the LOC, there is normally no requirement to use the aid for enroute track guidance so the output power is lower and, as a result, the rated reception distance (sometimes called rated coverage) is a lot less.
The LOC is often associated with an ILS as either the OM or MM, or both, which might be cheaper than installing marker beacons - though I could stand to be corrected on that point.
There's no difference from a procedure design perspective, except perhaps to ensure that the procedure keeps aircraft within the rated coverage of the LOC. Pilot tracking standards will be the same, whether using NDB or LOC.
I can't think of any situation where 2 different approaches are based on the same navaid and, in one, it's referred to as a LOC and in the other as a NDB. About the only thing that comes to mind is that, maybe, one procedure was designed some years ago when the aid might've be classified as, for example, a LOC, and the other procedure is more recent, perhaps as the result of an upgrade of the navaid from LOC to NDB.
Hmmm... having just re-read that paragraph, I'll bet it's as clear as mud...
