I would pick both as diversification is key to a long term wealth building strategy and to keep said wealth should disaster strike. Actually there are many other investments you should be looking into as well, I do not much like these either/or type questions as people should be expanding their investments, not narrowing them down.
I simply love bitcoins, but when it comes to an investment I would choose gold and not the bitcoins.
I have been into gold since long time, and gold has never disappointed me, everytime I invest it has given me some good returns on investments, so I choose Gold.