Honestly, I would not use SWU and bet on op-up instead. Op-up occurs very frequently (at least to me) during winter vacation especially on TPAC routes since Y tends to be overbooked and C tends to be empty due to lack of business travelers. As a result, they will move elites to C when Y is overbooked and as a 1K, you should be on top of the list.
But then again, like most upgrade, there's no guarantee. Roll your dice and hope for the best. As for ORD or IAD, I think they are about the same during the holiday season.