Clearly Bitcoins have a great chance to double, triple, or more in less than a year. Gold will not do that well.
Bitcoins have a great chance to be worth half, one third, or less a year from now. Gold will probably not do that bad.
the chance of bitcoin to going higher is above the change of it going lower, if you see the full chart from 2009 to today you will understand why
gold on the other hand is the definition of stagnant...
gold is not even stagnant if you look from 2011 till today. But gold's purpose is to protect what you have in the time of a total meltdown. This is very likely not coming in 2015, thus the answer what to choose is pretty simple.