We always have a real tree and put it up around the 15th December.
As for the real tree vs fake tree debate - aside from the fact that real trees are obviously much nicer and smell lovely, according to the soil association they are better for the environment, especially if you burn them afterwards.
The carbon footprint of fake trees is large - there's the manufacturing process, the fact that most of them are imported from China and the fact that they end up in landfill (after 4 years' use on average). Plus real trees benefit the environment and wildlife while they are growing.
Soil Asssociation article here