I thought the 5000 was meant to better than the 4000 because the drop size is 1pl instead of 2 pl. As both printers are only 4 ink as far as photo printing is concerned. no LM or LC inks, the smaller drop size gives a better output when printing the lighter colours.
I bought the 4000R as a general household printer. It was never meant to be a photo printer. However I am very impressed with its photo cababilities. I wanted a wireless printer so I had no choice, but if that was not an issue I think I would have gone for the 5000.
For true photo quality I think the 8 ink 8500 is the answer.