I have a proposition to make :
Print one negative on different colour papers (Fuji, Kodak, Eastern ones etc) and send them to me. I will place them on a rooftop in the center of Athens. They'll get 300 days of sunshine/year, pollution (NO's, SO's, Benzolium, heavy metals, CO etc etc) and acid rain (when it rains, that is rarely). In one years time, I bet most of them will have "gone"... we can then compare them to see who'll be the winner (if we can clean them of the filth that'll have been deposited on them).
The processing of the prints has to be the same, so it has to be ONE of you who'll print and process in the same RA4 machine at the same time.