Coming from a person with 52 zombie/walking dead movies
zombies don't shy from light, they are ATTRACTED to it.
Zombies are creatures of base instinct, they do not plan (even with the Romero series the zombies planning skills are on the low end).
Zombies don't sleep.
I am Legend "creatures" shy away from light.
Plan an attact/trap
Sleep
I think it's pretty much cut and dry..
(for the record, i believe they are just mutants, affected by the medicine, and able to be medically treated/cured depending on the ending you saw)