I think will I see if from a third perception. I feel SEO/SEM is more of Management than an art of science. Everyone has different strategy but follows same guidelines. It is not like science where you need to follow a perfect procedure to get the Chemical 'X'.
Yes it is science but only at google laboratory - where they create and modify the searching algorithms.
SEO follows management rules. You bind yourself to a 'schedule' to promote your site. You 'PLAN' your complete action 'strategy'. And time to time take review of it. You 'market' you site. You 'promote' it. See everything is related to management.
So, my vote goes to the third war front - Management!