To start it is important to get one thing straight about these printers. They are designed to make long lasting photography. You can use them for all sorts of projects, but keep in mind that they are primarily good at printing photos that will last many decades. Don't need that function? Don't care how long your prints will last? You might be better off with another dye based printer.
So if you decide you need long lasting prints, think about what you print most. Is it people, wildlife, landscapes, or other things? Now, think about what kind of paper you like to use most often. It's OK if you use other paper types, but be honest with yourself about what you prefer: glossy, matte, or watercolor papers? Next, do you primarily print color or black & white?
Taking these answers, check out the chart below for our suggestion of which printer to buy.
Potential problems that will crop up with both printers
For portfolio work, both printers offer great photo reproductions. The R1900 is certainly more vibrant in many respects than the R2880. However, the pigment inks in both printers offer a potential roadblock for portfolio printing: ink rub off.
Ink ruboff can occur between pages in a portfolio if the book is handled often or your photography contains primarily dark colors. These inks do not sink fully into the page, leaving a light dried residue on the surface. This residue can offset to fingers and other sheets in the book. We have seen this problem on many different paper stocks from various manufacturers.
To avoid the problem totally, we recommend portfolio printing with dye ink printers. Why make a portfolio that will last 50 years when you will replace it in one or two?
Bottom Line Recommendation
If you print primarily color on glossy and satin, buy an R1900. If black and white is at all important, you should seriously consider an R2880. Also for fine art work, portraiture, and printing on matte and cotton papers, the R2880 excells. If you can swing it, buy them both! It's still cheaper than a one good lens.
This suggestion is of course, our opinion based on using these machines with a wide variety of inkjet papers. Your experience may differ.