It was discussed in this thread but the difference is where exactly the bean is grown, ie; elevation/location and branding. Some folks will say they can discern a difference, others will say they cannot. I have heard some say they prefer the cheaper High Mountain to the more expensive Blue Mountain, although it is typically vice versa.
JBM is typically smoother which is attributed to the elevation of 2000 ft in the Blue Mountain range. HM can be a bit more bitter with various tastes as it can be grown anywhere.
And this can all be pure opinion, I have had instant coffee in Negril and it tasted amazing while looking out over the sea!





