Sun Tzu's, then Leo's, then Pyramids. Both are good, but the Pyramids are too early and one has better things to build, and the AI almost always beats you to it, plus the early growth could hamper you by having useless entertainers take care of the happiness problems you have with cities growing faster. It's usefullness appears later in the game. Sun Tzu's, on the other hand, provides a much better building, is at a stage in the game, where you're more likely to be able to devote time to it, and if you fail you might be able to cascade into Leo's, which is a very nice moneysaver. If you get both then you can immediately upgrade all your defenders and wage wars quite nicely