In my recent testing of the new FB type papers by the numbers, I've let QTR send calibration ramps of each ink to each paper, mainly to study their black and white response, but I also just checked these two papers for Magenta and Yellow maximums (no profile involved, just telling each ink to lay down a 20 step ramp to the maximum) with my Epson 3800. The difference between the two papers you mention is virtually nil, with perhaps a tiny bit lighter response from the Gold Fiber Silk. Both papers should give you equally rich reds.
Prints I've made of a volcanic fountain (from a scanned Kodachrome) with strong glowing orange reds are quite rich on both the Harman and the Gold Fiber Silk, such that the differences are mostly in the surface texture and gloss differential. Black densities (dMax) are also practically identical. It comes down to personal preference.
Almost all really good profiles have gone through some editing, and there may be profiles tuned not only to specific papers but to specific purposes as well. For a good discussion and example of profile editing see Bruce Fraser, Chris Murphy, and Fred Bunting's "Real World Color Management" second edition, published by Peachpit Press, 2005.
Your findings are very interesting and fall in line with my recent testing of 16 different papers from Hahne., Innova, Crane, Red River, and Harmon. I used a controlled setup also, printing from the driver using the same media type - "Special #5" in my iPF5000, which works with all feeds paths, for the eight "glossy" variants, and the all-path "Premium Matte Paper" for the true mattes.
In each group, each paper got exactly the same ink applied. I was looking to see the differences, which I thought would be obvious, and reveal something about the individual paper characteristics. But as the test progressed with two prints each of separate unmodified test images, I was amazed not only to see papers of a closely related type virtually identical in response (any differences directly correlating with paper whiteness or warmth), but also essentially identical output with papers as different as RR UltraPro Satin 2.0, Harmon Fb Al Gloss, and Hahne. Photo Rag Pearl and Fine Art Pearl.
Surfaces varied, of course, but with light behind the observer, each group was incredibly uniform, except for Hahne. Photo Rag Satin in the "glossy" group, which was very muted; and Crane Museo (original version) in the matte group, which did not take the ink well, but looked good except slightly muddy shadows after drying overnight. The two very inexpensive photo mattes (RR Polar and Premium Matte Plus) came off very well, the Prem. a little lacking in contrast and sat, but easily tweakable to be indistinguishable from the virtually identical premium fine art rag papers such as Innova Smooth Cotton High White 315 and Hahne. Photo Rag 308 (slightly more texture than the Innova), but much less that the German Etching, Museum Etching, and Wm Turner which also had identical color responses to my eyes.
There were differences between the two groups - all the "glossies" had significantly brighter reds, and again, virtually no difference I could see not related to paper tone. The mattes had identical slightly orangy reds by comparison, but Atkinson's luscious strawberries still looked plenty good in all. Basically, every print except with the Photo Rag Satin was more than acceptable.
I'm looking forward to getting Ilford Gold Fibre and Innova F-type series samples to complete my testing, then getting someone to do some objective measurements. Would you be interested Aaron?
My conclusion? Papers are incredibly more similar within their general group than I had believed possible. Certainly closer with this standard test than could be achieved with canned profiles from different sources; and likely, in my opinion, more consistent paper-to-paper than with custom profiles from the same source considering the many different surface characteristics and their effect on surface reflectiveness.
For more details, see my thread in the DP Review printer Printers/Printing forum: