What are the exact percentages for likelihood of getting 3 diamonds from a diamond ore with Fortune 3?
Solution 1:
From the minecraft wiki:
Fortune increases block drops. For coal, diamond, emerald, nether quartz, and lapis lazuli, level I gives a 33% chance to multiply drops by 2 (averaging 33% increase), level II gives a chance to multiply drops by 2 or 3 (25% chance each, averaging 75% increase), and level III gives a chance to multiply drops by 2, 3, or 4 (20% chance each, averaging 120% increase).
Sounds like the fortune pickaxe is the way to go.