For an estimate, you need to have a trained, experienced installer look over your particular situation. Generally, an electric system would probably be a lot cheaper because it could be a prefab. If you put up masonry, the cost would be higher, but then you could get a lot more heat, depending on the kind of system you put into the masonry fireplace. But is atmostphere and a pretty flame is your first priority, and you do not need a lot of heat, electric might be the best option.