I'm relatively new to DnD in general and 5th edition is my first experience with Dungeons and Dragons. I am confused with some spell mechanics.
Spells usually state that they do damage, such as:
Burning Hands (Lv 1)
A creature takes 3d6 fire damage
Ray of Sickness (Lv 1)
On a hit, the target takes 2d8 poison damage
But some spells only dictate that the hit points are affected:
Sleep (Lv 1)
Roll 5d8; the total is how many hit points of creatures this spell can affect.
Color Spray (Lv 1)
Roll 6d10, the total is how many hit points of creatures this spell can effect.
In this case what would I do? Do I do 5d8 of damage if I cast Sleep or 6d10 of damage if I cast Color Spray. If so why on earth would I use any other Level 1 spell as these two would be exponentially better than anyother DnD 5e level 1 spells?