With bitcoin you know for a fact, that there will be only 20999999.9769 bitcoins out there (maximum global supply ever), not a single bit more 
I guess it would take only a few minutes to change that condition (at least, there is a possibility of doing just that). You can't do that with gold by any means, no matter what you try, that is, increase the amount of gold by some arbitrary decision...
Even if you get consensus over that