If you could only invest in one, I'd say gold. As much as I love Bitcoin, its a technology in its infancy, theres no telling if its going to last long term. I think your chances of having a high return are greater with Bitcoin, however you are pretty much guarenteed at the very least some return on gold. Gold has been currency/an asset for 5,000 years. Bitcoin has been for 6 years.

If its not a one or the other choice, why not invest in both?