My husband and I are going to WDW December 10 thru 19th. We are thinking about booking a trip to Universal, too. We have done the one day, one park with purchased EP's before, and we have done the overnight stay at a deluxe resort with free EP's and 2 days admission.
Haven't made our minds up yet. Each trip worked out well for what we wanted at the time.
I am leaning toward going for overnight, free EP's, 2 days at Universal this time. It only costs us $188.00 more to stay overnight. One night at RPR is $308 with taxes, zero for EP's, $265 for 2 day PH tickets totals $573.00. One day at Universal Studios only for 2 is tickets, $205.00 and 2 EP"s $180.00. Totals: $385.00. So we need to decide if we want 2 days or just a day trip to one park. We like the studios more than IOA.
It surprised me how little a 2 days stay is. We would do this in the middle of our WDW stay.
Hope this helps.
As far as Christmas dec's? Have never been in December before, so no help there.