None would be the best answer...or one you can reuse every year. Be careful some of those fake ones are made from some toxic stuff. Always check the labels and if you are looking to save energy too go with one that has LED lights.
The Pros and Cons of real Christmas trees:
There are approximately 33 million real Christmas trees that are sold in North America each year, according to the U.S. EPA. It is good news to know that about 93% of those Christmas trees are recycled through over than 4,000 available recycling programs.
The term "treecycling" is the act of recycling a Christmas tree. For this reason alone is why many experts say that the natural cut trees are the more environmentally choice to make over plastic trees. It is an easy way to return a natural and renewable source back into the environment.
For more information please check out his article from Earth911.