I was looking into the relationships between man, fire, brain size, evolution, etc. and I learned about other methods of food preparation that eased digestion, but did not use fire. Then, this question popped into my head. Specifically, I am wondering how much easier is sun-dried meat to digest; how much of a benefit is gained in the amount of energy needed for the digestive process?
Depends on how you define digestion.
If you consider chewing to be part of digestion, then this actually makes it more difficult as dried meat ("jerky") is harder to chew (into small pieces that are easier to digest) and harder for liquid (including saliva) to permeate.
Otherwise, ease of digestion is best defined at the molecular level. Tough fibers tend to be difficult to digest; pure protein can generally be hydrolyzed except in specific cases of structures specifically designed to withstand digestion. No idea if sunlight causes significant enough structural changes to change how digestable the meat is - that would depend on if the sunlight causes chemical reactions that "tenderize" the meat.