in terms of upkeep costs? or for battle?
for the upkeep, simply just multiply each ship by a certain factor that would raise them to the same power, then multiply the upkeep by the number of ships, and compare their efficiency
but for defending, or attacking, each ship has certain advantages that transcend their ship class, so there is no "answer" to your question in those terms, whether smaller ships would be better to maintain (for battle) than larger ships