Oh boy, good question. Probably bitcoin simply because of it's speculation attributes. Also I think silver above gold (just look at the gold to silver ratio).
historically, there is still space to the upside on the gold/silver ratio. we are currently in the low 70s, the recent peak was at 80s, historical peaks within last 20 years reached 100.
And why bitcoin over altcoins, in terms of gain?
Historical average in the au:ag ratio is 16:1 (and since 1900, it has been ~27:1) so being in the 70's, gold is still in a bubble of epic proportions (or the suppression of silver is out of control...) More likely, it's both, really
take a look at the last hundred years of gold/silver ratio here:
http://www.macrotrends.net/1441/gold-to-silver-ratio-historical-chartthis ratio stayed above 70 all the time in between 1989 and 1997 (so being above 70 may be toppish, but doesn't have to).
Also, the last two peaks were closer to, or even above 80, rather than in the area we are right now. The third last one was the ATH, at about 100.
Bottom line, there is still room to push gold lower (and silver even more) and that won't be against any historical trends.