the fortune is capped to 9 melon slices I think so you will not make extra money is you reconstruct them I think that is...
Silk Touch is definitely better. It will always give you a whole melon (9 slices) while Fortune will give you less occasionally. It also saves up time upon having to craft the whole melons, and helps you save up space on your inventory.
quefueve said I do aggre with quefueve i used to not have a silk ax and all the melon slices took up a lot of inventory space
Pick is better! I've done a bunch of research and testing, and pick is better than axe on melons. Actually, sword is supposedly best on melons, and axe is best on pumpkins. However, the enchantments best for melon farming aren't available on swords (obviously ), so pick is the second best. Anyway, I use: Efficiency IV Unbreaking III Silk Touch I Diamond Pickaxe