national vs local fraternities question

Just wondering how national and local fraternities here at Dartmouth compare in terms of strength of alumni network. I could be wrong but it just seems that a single chapter worth of alums - with whom you already share the Dartmouth connection - can't really compare to the tens or hundreds of chapters at different schools you get with a national organization. Obviously there are cons to being national and this is just one of many important things to consider when choosing a house, but it's something I've always been curious about so I'd really appreciate some insight.