Cheaper, better, "better if" the problem is larger than minor repointing. You have enough at stake here that it would be worth a call to a local mason to ask this question. I suspect that although the problem has been described as minor re-pointing, the real issue may be larger. If bricks are failing or the chimney needs extensive work the covering with stucco or concrete is a cheaper solution and will make the chimney serviceable for a number of years. I would get a professioal opinion on the integrity of the chimney and a recommendation. I would think that the cost to have a mason inspect the chimney and provide a written opinion would be your best bet. My guess is that the sellers are only required to make the chimney serviceable, but you need to know the long term cost implecations. Remember that you may need to pick up part of the cost if you ask for more than the minimum necessary repair. But all things are negotiable.