I, personally, would need more info. Smith's is good if you are in desparate need of money and have built/will build those improvements.
Questions: Are you a big civ? How many luxuries do you have? What level are you playing at? What gov't type are you now and do you plan to be at Democracy long?
Sistine can be invaluable at helping the happiness factor. If you are weak there, Sistine could help bring up happiness, while eliminating the need to change the slider and spend gold to keep people happy. In this case, Sistine's would be much more useful. Also, if you plan to be in democracy and war for any length of time, Sistine would be more important.
Not knowing your exact position, I would sum up as: 1. If money is your overriding concern - Smith. 2 If Happineess is a problem or will be if you go to war - Sistine.