I thought I clicked the button for the Canon forum for a moment when I read this threads title.
Come on, you can't possibily compare noise with resized photos shot under completely different lighting conditions, foca lenghts, apertures, etc...
Something closer to the truth will be realized a lot more in the resultant printed images with 99% of them being done at 8 X 12 or smaller sizes.
Any IQ or resolution advantages the much larger 5D sensor might have will just not be fully appreciated by the masses these two cameras are marketed toward.
Images blown and shown at 100% on screen or printed at 20 X 30 will have to be pixel peeped to expose the differences anyway.
Someone will always be reminding you that the marginal gain simply wasn`t worth the cost. ( rule of diminishing return)
John