retina versus non-retina

I have a dilemma, i’m about to buy one of the new macbook pro’s recently launched. But as i am a blender user my choice depends on what the gpu can handle. Is it possible to render in cycles in gpu mode with this new iris card or will it still be a cpu render. In that case , is it so that the non retina with intel 4000 graphics card would give the same result ? Iow, what’s the relationship between the two new graphic cards and the use of cycles ? Until now there is little testing done on the web.