Soda robs your bones of calcium. It plays around with the acid/base balance of the body. These two things are true even when there aren't sugar or sweeteners to contend with.
Coffee does contain caffeine. If ingested lightly or moderately, along with a healthy diet and other liquid intake, it can have true benefits to the body. Some people drink it with half and half, and limit fat consumption at other times of the day. It's a great strategy to level off blood sugar first thing in the morning. There's a small amount of sugar in half and half, and enough fat to sustain until food can be ready.
Coffee can be prepared as an iced beverage, with milk, half and half, or black. A decaf version of the same drink is delicious. Stevia can be used to sweeten.
Coffee wins the contest.