The 5006 trades off a lot of digital formats (and other goodies) for internet connectivity. If the 5005 had internet connectivity, the 5006 would be a serious downgrade. I'm putting my money on the 5005.
However, beware. Again, remember the refurbs had a defect to start with, and from reviews they occasionally show up after extended play times. Apparently Marantz isn't letting the units "burn in" overnight before testing the units. Heard one horror story, guy received 2 defective replacement 5005s from Marantz, and finally caved and took his money back and went almost three weeks without a receiver.
On the up side, accessories4less offers a 5 year warranty for only $50. Personally, I think I'll drop the extra $150 and buy new, with a three year warranty.