This all depends on just how specific you’d like your filtering on your site.
Personally- I’d have a category for the main systems (android, ios, microsoft, etc.) and then a sub-category for Make/Model of phone (iphone 7, iphone 6s, droid maxx, etc.) and then use attributes for the color and processor(black, 32gb, etc.).
However, that is going to depend on how you want the site set up. It also depends on if you are using the standard woocommerce search built-in or a search plugin (some will search through tags, attributes and short descriptions), or a category filter.
Think about when you are shopping, how do you normally search? Or filter?