What is your definition of "Mecca"? A single range that is awesome or a location that has lots to offer overall?
If it is a single facility, the considerations would be number and quality of firing points, club house, amenities, availability of practice ranges, location, etc.
For a location, it would be number of matches available per month, availability of year round matches, availability of practice ranges, weather, local talent, big matches in the area and general community quality.
The first has been discussed briefly in a thread about the best range. Not a lot of responses.
The second has been covered by many threads about the best place to live for practical shooters.