This is a tough call,
My experience is that I bought a near new epson 7800 from a guy who was tearing his hair out with it.
For me the 7800 has performed flawlessly, it left my place in Brooklyn, via container to London and I just plugged it in and off it went.
Some pointers:
I print mostly on IGFS or now the Canson Baryta Photographique
I print through Lightroom/ epson driver
I print 24" rolls, large sheets down to a4
I use epson inks only
I don't print all the time
The printer is always on
The office temperature is stable all year round.
I love working with this printer, the epson driver is dated now but keep it simple is a good method of working.
I have seen in these forums that the later 7880/9880 printers clog more, mine 'never' clogs and seldom needs a quick clean.
One little thing I like is that you can buy a chip re setter and replace the contents of the ink waste tank yourself, it's definitely not nice chucking away a solid plastic box that can easily be used many times.
Hope this helps.
S