I've already posted my contribution to the session, but some others' thoughts and more musing on my own means I've got some more to say on the subject whilst the platform is provided by the session.
Beer is a local product. It is made local to somewhere, often in only one location, with local employees.
Beer style can be influenced by local traditions and climate. Think lambic in lembeek, Sahti in Finland and Weisse beer in Germany
Yeast adapts to local conditions to give local taste to beer
Different locales interpret the same beer style differently often giving rise to interesting variations as discussed re. Brown Ale by Boak & Bailey this variation can even give rise to a new style of beer...think hop-forward IPAs from the American West Coast in comparison to those brewed in the UK.
Local beer is often fresher. It is well known that some beers are said "not to travel well". Whether this is lack of freshness, conditions of carriage or simply an inability to perform quality control so far from the brewery local is best. Before the advent of cheap distribution people would travel to other areas of the country to sample the local beers. We're somewhat spoilt now as the beer is brought to us and we perhaps lose something in the process.
Shorter distribution miles generally means the beer is fresher and hence better. Why else would American brewers be looking to set up shop in the UK?
Breweries get involved in local events and in turn local people buy local beer in turn improving the local economy and general well-being of the local area.
Local brewers can often use local ingredients. This can help local farmers and often a symbiotic relationship can be formed. Although you should perhaps be wary of brewers claiming use of local malt is inherently more environmentally friendly. Often this malt must be shipped to a maltings and back to the brewer, in effect doubling the transportation miles. (Breweries when taken over often have production of beers shifted to other outlets; so also not necessarily local).
95% of beer's volume is water..another local factor of beer though with liquor treatment this is perhaps now provided for. Countless scores of brewers look to produce the local water of Burton-on-Trent in the process of Burtonisation.
All of these factors ensure that beer is a local product; so its not so much that local beer is best, more so that beer is best.