Quote Originally Posted by surviva316 View Post
Of course, maybe there is a margin between the ice's temp at t=0 and its melting point (say, the ice cube is initially 25 degrees F), so that when the heat loss of the drink is dispersed over a larger area, less ice actually melts initially. Latent heat would also possibly cause this, so that energy is being spent on too many places at once which is causing the melting process of any one molecule to slow.
I missed this part about the ice starting at a temperature below the melting point. You are correct that the temp change of the ice up to the melting point would cool the drink without causing melting of the ice. As long as we start with identical ice cubes for both beverages, though, the answer I gave still holds.