Imagine you have a pile of snow and a pile of ice shards. You put a soda bottle which has a room temperature into both piles. Which bottle is going to cool down faster?
This depends on contact area between bottle & ice/snow, and consistency of snow.
If there is not much air in the snow, it should have bigger contact area with bottle, and thus heat will be transferred faster.
Ice will contact with the bottle mainly at shards edges, so contact area is small.
PS. Adding water will change everything, as contact area would be maximized in both cases.
For one you must define room temperature. because if the bottle is worm enough to to slightly melt the show first and then refreeze then this one will cool 1st of not the air in the snow can act as an insulator and this one will take longer. Now the shape and sise of the ice will make a large contribution/small to the surface contact on the bottle this will also make a difference on the air flow around the pieces of ice.
You need to make the experiment MUCH more specific to get a correct answer.
The first thing to realize is that "ice" is a pile of small ice shards and snow is a pile of itty-bitty ice shards.
Assuming the snow and ice are at the same temperature, the answer to your question with come down to which one has more contact area and (to a much lesser extent) how that contact area is distributed. Also note that the contact area and its distribution could change over time, as the can melts the ice/snow.
You'd have to run the experiment. My guess is that ice would be the winner. This is because ice would maintain a much larger contact area over time. The can in the snow would melt the snow beneath it and drop away from the "snow roof" over it; whereas I would expect the "ice roof" to collapse with the can, continuing to cool it. The can contents in contact with the roof would be expected to be the warmest, thereby giving maximum cooling effect from any contact on the top side of the can.
Thermal conductivity of ice is higher than thermal conductivity of snow, so ice is the winner. Ice has higher thermal conductivity because it is more dense than snow. When snow is as dense as ice then it is no longer snow, it is ice.
Thank you for your answers, without them I wouldn't guessed it right :) .