I love to express when there are no correct answers!
I voted for work/ex and company brand for the following reasons:
1.) Most of the factors that you mentioned, directly or indirectly are 'based' on your work history. You are nothing without the work you have done. Your essays, recos, interviews etc. are, primarily, a derived factor of your resume.
2.) I will put my faith in a person from McK than in a person who says he is brilliant but does not have a brand backing. And I'm sure so will the adcom. The person from McK has already been selected out of a competitive pool, has worked with the best minds, has worked on the best projects and frankly, brings a LOT more to the table.
3.) Your GMAT essentially explains your ability to do well on a standardized test. It can keep you out, but does not guarantee admissions. And the fact that most of the qualified candidates do get a good score (the ethic made them a strong candidate in the first place), does not make the GMAT very important when we talk about the M7s. Having said that, obviously a 99% goes a long way in saying that you are very serious about your MBA.
4.) I sometimes feel the essays are over-rated. I haven't seen a lot of candidates without extra ordinary credits get into a big school. That only explains that essays are a medium to explain what you have already achieved in your past life. There are few qualified and sane candidates, who outright screw their essays.
They are obviously very useful when you are comparing similar qualified candidates - but, again, we are assuming that both have an exceptional work history, which makes the essays sort of a 'tie-breaker'.
5.) I look at the work history as a long process, drawn out over the 5-6 years of one's career. I think its a much better indicator of the pedigree than the GMAT - that's written in a day (and prepared over 3 months) and essays, which might have consultant's input - not saying it is wrong to use them
Anyone may rip apart the above points because they generalize a lot of things. But, in essence, this is what I've gathered till now!
This comes from someone who does have a 99% GMAT, but is still skeptical of his chances!