Actually I think the most festive park for Christmas in Orlando is SeaWorld. They own Christmas (really decorate for the holidays, lots of special shows and theming -- really incredible). It's the park we always choose for Christmas day when they whole family is in Orlando for the holidays. // Sounds like, though, you are just looking for a Disney Park suggestion. If you have any inclination to try SeaWorld, I highly recommend it for a great Christmas experience.
With just one Disney Park day, I have to cater to the family and it's the classic Magic Kingdom park every time.
I'll defer to others comment on hoppers, as I only got a one day park hopper once. For that we did the MK at rope drop, stayed there till 2 p.m. and then hopped to Epcot. We did the MK on a party day (if you don't need the night time fireworks there this is a really good choice as most people want more time, so party days have light daytime crowds). Epcot lines were pretty long for attractions and we were only able to get one fastpass for what we wanted. And then as DS really loves Test Track, we skipped Illuminations and rode that three times the line was really short during Illuminations. We actually had a good time just wandering around the countries when the lines were long, though too.