Probably the best resources for comparing the comparative advantages/disadvantages of the two modes would be some of the technical articles and debates between the NYC/GE-backed DC camp and the NYNH&H/Westinghouse-backed AC camp that were published in Railway Age, the Street Railway Journal, and other trade magazines back in the early 1900's when the question of what method to use when electrifying the routes into Grand Central Terminal were the subject of some fairly heated arguments. While the actual costs today would be very different than they were 115 years ago, the relative costs of one vs the other probably haven't changed that much.