well digging resources may be more profitable but what when u digg all iron on site and cant find more for that day or days ion other hand farming melons can provide u with maybe less profit but constant one
u can farm your melons every day all day.....as long as u got big farm or multiple farms .....only farms are best to protect using cole ore protection stones so that griefers dont took u'r melons and devastate entire field by cuting stem or/and digging holes and pluging u'r water holes
(
i learned that after my nonautomated farm with over 80 stem's was destroyed in that way by some mentally unstable full of jelaousy child who finds satisfaction only in destroying what they havent maded.)
Protected melon farm gives u constant flow of money unlike finding more worthy iron which can be used in crafting:bucket,gear,tools for digging diamonds,steal doors that zombie cant break,compass etc.