Well in my opinion it's a hard pick as there are both limited resources of both so eventually they will be rare commodities, so either will be valuable...
In my opinion, Gold is worth something no matter if it is the year 1000 or the year 5000...So in my personal opinion gold is the better option. Bitcoin is no doubt the best digital commodity, but digital can always be wiped out and thats not a risk I would take if I had the option to own gold over bitcoin!