it all really depends on exactly what you will want from it. future mods, tuning adjustment, how much you want to spend, etc..
They are all different and better in their own ways.
It's all been covered in various treads, so i suggest starting with spending hours reading through them as most people won't want to repeat themselves again and again and again. Recently I have read about some nistunes not working for unknown reasons also some PFC having problems with the not so old models, as compared to the old ones, lol..
But basically you first need to know what you want in the end, then find the appropriate steps to get there. Or at least an idea of what you want from each piece as you source it..