One is a longer process than the other, also one is more toxic.
They both have an egg cell wall, a vacuole, and chloroplast, smooth and rough ER, and much more.
Onion skin is treated to be a tissue because it is thin and - brittle.
The skin cells of the onion get a well which gives- the outer portion its rigid shape.
Though all choices protect your organs the most important would be your bones.