Larry,
I few more thoughts on the 7900/7890.
I owned (3) 9880's over the space of 4 years. I never had more than one on line at a time. I loved the fact that I could print with the Atkinson profiles on the 9880, his last set that were generated for the 11880 were top notch. My 9880's had terrible skewing issues, enough of a problem that Epson finally agreed to replace my last one with a 9900. I had held off purchase of the 9900 mainly due to the issues around the 1st years or so of shipments.
I believe your question was can you tell much difference between the output of the 7900/7890 series. Ink wise, the 7890 and 9880 are the same (except you can have the MK and PK online at the same time). The head is different (I believe it's the same head as the 7900, but the orange and green are mapped out but can't confirm that) All the other specs are the same.
With the 9900 I was hoping to see the following:
1. Less gloss differential
2. Less bronzing
3. Less soft proofing issues
After using the 9900 for 3.5 years now:
1. Gloss differential is still a very big issue, I can see no difference. I have a series of actions that I use to help reduce it on prints with a lot of areas where gloss differential seems to really show up.
2. Bronzing, really about the same, maybe a bit worse but for sure very paper and profile dependent. One of my favorite papers is the Canon Platine, but bronzing with it is very harsh depending on the print.
3. Less soft proofing issues, let me just say, no. I still have as many issues there also.
My print is 3.5 years old, and I have gone through 6 sets of 700ML carts for all the other colors. My starter cart of orange and green lasted 1.5 years and I just finally replaced my 350ML set of orange and green, purchasing instead 150ML size. I am sure the green and orange have an effect but to my eye on m prints I just can't see it. Older prints from my 9880 on platine that I have reprinted on 9900 and Platine, just don't seem to have a viewable difference to me. I am basing that on my eye.
For me, the single biggest advantage the 7900/7890 have is the ability to switch to MK or PK without a massive loss of ink. I print a lot of matte canvas, but all my paper is glossy or satin. So I switch pretty much weekly. So for me I see that as a huge advantage over the older 9880 family. The 7900/7980 are faster, for similar a bit better overall details. My 9900 still occasionally does skew, but that tends to be from a roll of canvas that was not placed on the roll evenly.
If I had it to do all over, based on my prints, I would go with the 9890, and forget the orange and green.
Paul