the 27th is the Monday after Thanksgiving.....so i wasn't sure if that would be tough for people (although it might not be too bad, because all the Thanksgiving planning is out of the way)
but then the 13th is just around the corner (in a way) - so less time for planning
I would rather the 13th just because its so close to thanksgiving...but what time is the party? if you are expecting people to take off work it may be cutting it close