At this point, changing either icon would cause greater confusion, as they have been in place for several years, and other users know them. I would recommend customizing the CSS if you have a different icon in mind.
To be frank, we struggled with this when the "views" icon was implemented. We could not find a better icon in the FA set, nor could we change the existing hide/show icon to something like +/-, because that FA eye already been in place for that for 3 years and the +/- was already in use as well (elsewhere for add/remove controls). I wish you luck in finding a solution that works for you.