I have a few pictures that depend on transparent sky gradations in the blues through reds that print a lot better on the iPF8300 than on the old 8-ink 9880. But for a lot of images, those two printers produce essentially identical prints. I don't do much flesh photography, but I can guess the 12-inkers might do a lot better on skin tones than the 8-inkers, given good files and wide gamut media.
And for a few brutally over processed shots from years ago, the lower gamut 9880 rendition is actually "better" by some criteria, compared to the iPF8300 renditions which shows up how bad the overprocessing actually is. Classic cases of a newbie scratching his head while pushing images ever farther outside their gamut limits, until finally the out of gamut printer flummoxing becomes a part of the image. Although I could probably realize some improvements from the 9880 versions by reprocessing the shots with the iPF8300 in mind, I probably won't do anything beyond some desaturation because the images are too well known in their present overwrought forms. So what I'm trying to say, going 8-ink to 12-ink can potentially have some complications for those with old image libraries.
But beyond gamut considerations, I would advise choosing a low mileage printer over a high mileage one. Sooner or later a printer will need a very expensive service call, which can easily add up to some real money.
