I have been comparing the stats of the different spells and i am a little stumped as to how the drain has been decided.
Blast is Indirect Physical stun at line of sight does F drain (AOE)
Indirect can be dodged, but does greater damage
Physical means no spirit can be hit by it
Stun means can't damage machines
Ball lightning is indirect elemental physical damage at line of sight that does F-1 drain (AOE)
Elemental means extra effects or damage (linked to the element)
Damage means it can affect unliving targets
Assuming you don't need to stun, "Blast" sucks.
Why is "Blast" more draining than a better alternative?
BLAST (Indirect) Type: P Range: LOS (A) Damage: S Duration: I Drain: F
These spells smack the target(s) with invisible psychokinetic force, similar to a bruising punch, that inflicts Stun damage. Punch requires you to touch the target. Clout affects a single target, while Blast is an area spell.
Elemental attacks (they all have same stats anyways)
BALL LIGHTNING (Indirect, Elemental) Type: P Range: LOS (A) Damage: P Duration: I Drain: F – 1
These spells create and direct vicious strikes of electricity that cause Electricity damage (p. 170). Lightning Bolt is a single target spell. Ball Lightning is an area spell.