So i'm going to answer to my own question. I just bought the Series S and the console finally passed the stress test. I come from One X. Verdict : it's night and day. First thing first : the Series S is running the One S version of the game. So yes, it's blurier than on the One X, less detailed. However, on the other hand, well, it's just a new way to experience the game. It's smooth, running insanely good compared to the old gen. It's around 60 FPS, and coming around an Island, even a huge one with massive constructions, ships and shipyards, is not a problem anymore. It's almost perfect in terms of performance. So yes, the Series S delivers a massive improvment. Oh and the music isn't lagging anymore and the loading times are ridiculously short.