What's stupid is saying this is only about resolution. It's not.
Resolution is one item in the triangle between "resolution * framerate * complexity"
More GPU power in the form of TFLOPs, #texture units, #rops and memory bandwidth means you can do more of any of those things on PS4.
A) At the same resolution & complexity PS4 can do a higher framerate.
B) At the same resolution & framerate PS4 can do a higher quality.
C) At the same quality & framerate PS4 can do a higher resolution.
Most multi-platform games currently use option (C), but Tomb Raider uses option (A) - same resolution, much better framerate on PS4.