This is a stupid test that I did to show you how all gpu softwares render the noise differently.
The model is a simple room 5x5x3 meters with a rectangular aperture of 0,5x0,5 meters.
On the floor several big teapots with plastic, metal, glass materials (no dispersion). The walls have a diffuse white material.
The camera has 2.8 of aperture, 400 iso, 1/100 shutter speed.
The light comes from the hole on the ceiling. Proprietary Sun+Skylight for each scene.
3507x2480, 3 hours of rendering, 4 gtx580 used.
Please notice the noise:
Arion: noise really compact, very good and smooth
Octane: noise very good and sharp
iRay: noise with checkerboard artifacts under the glass teapots
Vray: bands everywhere, render unusable