http://www.ign.com/articles/2014/10/06/assassins-creed-unity-locked-at-900p-for-both-xbox-one-ps4

Ubisoft's upcoming Assassin's Creed Unity will run at 900p regardless of whether it's the Xbox One or the PS4 version. The framerate, too, will be locked to 30 fps.

Senior producer Vincent Pontbriand said that the reason behind the decision boiled down to wanting to "avoid all the debates and stuff." He went on to explain the technical reasons behind the decisions, telling VideoGamer.com that the lock in graphical performance had to do with the console's CPUs and not GPUs.

Saying that the CPU processing the AI in the game while also processing the number of NPCs on the screen presented a bottleneck.

"It's not the number of polygons that affect the framerate," Pontbriand explained. Rather, the tradeoff comes when deciding to keep either a high framerate or convincing AI. He said that they could be running at 100fps if they only had to take into account the graphics, but the AI demands on the processor have moved them to lock the framerate at 30fps on both console versions.

The Xbox One and PS4 versions of last year's Assassin's Creed: Black Flag both initially ran at the 900p resolution, but a later patch bumped the PS4 version up to 1080p.

OMG, run it in 640p if you have to, just give us 60 fps, dumbasses