I've owned the PSB Stratus Silver i's and I've heard the Gold's, as well.
First, let me preface this by saying that both of these speakers offer outstanding bang for the buck.
The Gold's have a deeper, stronger bass presence than the Silver's. The Silver's, on the other hand, seemed to have a more delicate midrange, but the Gold's overall have a deeper, fuller presence.
The silver's are also easier for an amp to drive. According to a friend whose audio opinions I trust implicitly, the Gold's require that rare amp that can tightly grip the woofers in order to achieve their true potential.
Both are great speakers. The decision comes down to how much you value bass and whether your amp is up to the task.
Michael