First up, let's compare the two versions of the game running exact like-for-like footage via engine-driven cut-scenes. On Xbox One, we see a lock at 30fps, with occasional dropped frames shifting results lower. Activity is far more interesting on the PS4 side though, with frame-rate varying from anything between 32fps to 60fps across our sample, with elements such as TressFX, depth of field and transparent alpha effects hitting frame-rate in a cumulative manner. Note in particular how scenes that switch between the TressFX-enabled Lara and the rest of the cast can see sudden switches in performance.
From synchronous rendering in engine-driven cut-scenes, we move on to actual gameplay, where we capture action from the same areas of each version. Clearly the results here won't represent exact like-for-like testing, but they do give us a better indication of how each version actually plays. There's a 71 per cent frame throughput boost on PS4 in these tests that owes much to the unlock, but a remarkable variation of 33-60fps across the run of play. For its part, Xbox One is clearly more consistent, but a lowest reported frame-rate dip of 24fps isn't great.
The overall feeling we get from the game is that two different developers handed in two different performance levels, and decisions were made on how best to work with the results. With the PlayStation 4 averaging at 50fps and often hitting 60fps, frame-rate was left unlocked, producing the markedly higher results you see in the tables above.
For Xbox One, we can only speculate, but we suspect that a lower overall performance resulted in even more noticeable judder were the game to remain unlocked - which would look really unattractive compared to the capped 30fps frame-rate we see in the final game. What's curious from our perspective is that United Front Games on Xbox One would have benefited from a reasonably straightforward porting process from the original PC DirectX 11 code since both platforms use the same API, while Nixxes would have needed to translate the original PC version across to the PS4's LibGNM API - not exactly a walk in the park based on this presentation from Ubisoft Reflections, who are handling the PS4 version of The Crew, ported across from the PC DirectX 11 codebase. Another development source we reached out to suggests that the DX11 'driver' for the Xbox One still requires a lot of work.