Disputing the above poster. Following info is from
http://www.crys.org/everquest/spells.htm which has Luclin-era data. MP ranges depend on level, with highest MP being at level 60.
Canni 1: 20-28 MP for 50 HP: 0.4 - 0.58 ratio
Canni 2: 30-36 MP for 67 HP: 0.45 - 0.54 ratio <-- LEAST EFFICIENT
Canni 3: 39-41 MP for 74 HP: 0.53 - 0.55 ratio