If you want to get really tinfoil hat about things, arable land and guns would be better than either gold or bitcoins (quick, to the Compound in Montana!). And if you don't want to get tinfoil hat about things, there are far, far better investments than either one - including, once again, land.
Really depends on what part of the world you live in, as to whether that's quite so tinfoil hat or not.
The most valuable thing you could get in those places is probably a ticket out. And dollars are probably easier to use to bribe/pay your way out - everyone recognizes a 100 dollar bill, but $100 of gold is pretty small.
Don't forget antibiotics, antivirals, and narcotic painkillers for your zombie survival kit...