Its currently unknown is how the Series S compares to the One X. I believe official specs aren't available yet but the GPU on the Series S is said to be slower than the current One X, while the CPU and memory are faster. The Series S has a few other modern features that will speed things up overall. We'll wait and see but it wouldn't surprise me if the the raw graphical performance ended up being not that much different. However I'd imagine the similar architecture to the Series X means that next gen games designed first and foremost for that machine will play better on the Series S than the One X. But given what's been shared, I dont think One X users upgrading to the Series S will see the kind of jump we associate with a next gen console.