I'm not an emulsion elite (I use both surfaces), but I have to comment.
6. I agree that the longetivity of photographs is very important for family matters. I am blessed with thousands - all on fiber, of course (and not selenium toned) - going back to the 1880's. But let's face it. Every print coming out of one's darkroom is not a "keeper." In fact, probably 95% have no value beyond the emotional one of the photographer. The world and our future generations are, for the most part, not waiting with bated breath for your latest. (Nor mine, I most humbly concur.)
If you're going to be pedantic, I'm going to be pedantic. "Every print...is not a 'keeper'" does not mean the same as "Not every print... is a 'keeper'". Some of my prints are keepers. I don't always know when I make them which ones will be. If I print all of my prints well, they will last if it's important that they last. Unless the cost to make them is significantly higher, why wouldn't one err on the side of caution? Using this logic, one could choose to be sloppy on exposure on the grounds that there is a 95% chance (using your numbers) that accurate exposure won't matter anyway, since the image won't be a keeper.
9. Polyethylene is one of the most stable, inert substances known to man. It will be in the landfills for thousands of years. If the PE barrier is well made, there is no reason that the emulsion should ever suffer effects of any low grade paper behind it. And do you really think that the FB paper companies selling to Ilford and Foma and everyone never have batch variations in quality, ISO 9001 not withstanding?
*If*. Products can be and frequently are made defectively. What defects can be introduced into fibre-based papers that would cause degradation? Probably there are some, but they are much fewer.
13. Kodak claims, for their latest papers, "Over 100 years in typical home display , Over 200 years in dark storage." Sounds pretty damned long term to me. Heck, my longest term dark storage is about 120 years only now. I ask, would The Great Yellow Father lie to you?
No, but the Great Yellow Father has an economic incentive for us to buy its products. I understand that accelerated aging tests can be made that will give an idea as to the longevity of a paper, but the only way to know if a print on a certain paper will last 100 or 200 years is to make a bunch of prints and store them for 100 or 200 years. Niépce's prints from the 1830s still exist (at least a handful of them), giving evidence that, even with the horridly incomplete knowledge of the time, silver-based photographic images can be stable for centuries. The jury is still out on the longevity of RC papers. We know for a fact that some RC papers have been horribly unarchival. We know for a fact that today's RC papers do not closely resemble those papers. We do not know for certain that the changes made absolutely solve the problem. We strongly suspect that they do, but we cannot and will not know for a long time.
Hey, I love the feel of fiber, too. I print keepers on FB, too. It just seems like the right thing to do, no doubt some deep, gene based compelling reason. It doesnt mean that that is the superior thing to do.
I think it can be argued that it's superior. There is nothing inherently wrong with superiority and inferiority. Fresh British Columbia wild salmon kicks the posterior of canned sockeye. The latter, however, is much more convenient, more readily available here far from the ocean, and much cheaper. It's vastly inferior but, for some applications, still adequate. I'll let the photographers of this site decide how inferior RC is to fibre for themselves, but if we are using the archival properties as our lens, there is reason to believe fibre is superior. For many images the tonality is superior (this is very easily tested). There is also a certain cachet incurred with using it, which has nothing to do with how desirable it is as a medium, but no doubt contributes to the debate. Once an image is framed, people can't tell if my images are RC or fibre (maybe some of you could, but usually not) so the cachet argument is rather moot, too.