In an interview with IGN, Crytek President and CEO Cevat Yerli stated that CryEngine 3 "will run slightly better" on the PlayStation 3. The difference may be negligible to gamers themselves, however, as Yerli also remarked that "it'll look and feel probably the same" on both platforms.
"The CE3 runs currently at more or less the same quality bar," Yerli asserted. "I say more or less because the engine still optimizes itself to power of the platforms' intrinsics. So the PS3 will run slightly better here, it'll look and feel probably the same, but the engine is diverting computation needs to power subsystems available to the PS3, and the 360 differently, and PC differently."
Yerli seemed a bit unsure of himself, but it's nice to know that the engine will, at the very least, run equally well on both platforms.