Even though PS4 and Xbox One share similar specs, one console has a leg up
This article discusses the many similarities the Xbox One and PS4 share. The two consoles diverge sharply when it comes to their GPUs. The Xbox One's GPU runs at 853MHz while the PS4 GPU runs at 800MHz. However, the PS4 GPU has much more hardware behind it—18 of AMD's compute units (CUs), rather than the 12 CUs in the Xbox One.
So what does this mean? Well, not much in the short term, but PS4's beefier GPU will give it the performance edge in the long term.