I vote for #8 by @ir3k because of its catchy title (permlink) and not the generic one ("steemit-ultimate-challenge-8-weeks"). Plus it specifically mentioned "steemit communication" which is what this contest is about.
If you check most of the post submissions, they have the same title. However for this one, she took it a step further and added a descriptive one.
Second factor is that it's on top of the list and can be easily checked and read.
Third, I checked the post and I do believe she deserves to win because she has already involved her family.