I think An Ancient World won because it's rated 3.9, while Bubble Wrap's rating is still TBD. Don't quote me on that though. Probably wrong.
Not that I know for sure, but it is unlikely to be the tiebreaker. Since in theory two (or more) maps could have the same rating. I would think it is the order in which the maps are nominated that is the tiebreaker.
Map of the week discussion: Week 115: 3/26/2017 02:56:23