Two Things
One, both the light and the darkness affinities had the same number of spell available for me.
Two, their category was more or less the same.
If one looked from a bystanders point than they will easily be able to figure out that they had almost the same effects and category.
Light Sword > Darkness Blade ( Close Range Spell )
The light affinity was a Sword type Spell and the darkness affinity was a blade type spell.
Light Bullets > Darkness Arrows ( Long Range Spell )
Light Bullets was from the Bullet type Spells and Darkness Arrows was from the Arrow type spells. The Light Bullets shot small and multiple bullets and Darkness Arrows shot big and also multiple arrows, the difference was that one was a little small and weaker but faster than the other one and the other one was big and more powerful but had less speed.
Light Shield > Darkness Cocoon ( Defensive Spell )
