Raw Spinach: contains nutrients, some of which are more available to our bodies when we consume them raw (eg folate, vitamin C, niacin, riboflavin, and potassium).
Cooked Spinach: contains nutrients. When you eat spinach that has been heated, you will absorb higher levels of vitamins A and E, protein, fibre, zinc, thiamin, calcium, and iron. Important carotenoids, such as beta-carotene, lutein, and zeaxanthin, also become more absorbable.
With respect to lutein (the stuff that is in dark green leafy vegetables, and is good for eye health) while raw spinach might contain more lutein, microwaved spinach has it in a more absorbable form (and microwaved spinach contains more lutein than boiled or fried spinach).