I think that Sage's Training is the better of the two. In this format, the need for speed surpasses all other things, and Sage's is just that. I hear some people saying that they like Cheren better in trainer lock, but I still think Sage's is better even in these kinds of decks. The only trainer lock decks really run is The Truth and Gothitelle, and those decks REALLY need to get the T2-T3 trainer lock in order to be able to continue setting up. In slower decks that dont take very long to set up, such as Durant, I think Cheren is better as they dont need as much help to set up and it would be worse for things to be discarded.