Silica Vs. Rice

Go with the silica gel. It's inert, non-toxic, won't mold, dust-free, and insects won't find it edible. Also, it's a one-time purchase since you can recharge it in your oven whenever it becomes saturated with moisture.

Yay silica gel!

Several things to consider.
With silica gels or such products, evertually you have to throw them out. With Rice, if no longer wanted for moisture elemination, you can now eat it.
If mice get into your coins and eat the Silica, they'll get sick and die. With Rice, the mice will get healtheir and reproduce even more.
Silica Gel packs are rather a complete item and you don't have to put them in anything special. Rice has to be put in something similar to a bowl or something.
Of course those Silica Gel packs are expensive and you can buy Rice by the hundred pound bags really cheap.
I don't use either. I keep many coins in my basement and use an electrical dehumidifier. They remove hunddreds or mayibe thousands of times more moisture than Rice or Silica.