Though there is one thing in favor of the Canson BP. I can quote Canson and say that it is acid-free, museum grade, complies with ISO 9706, internally buffered... My clients like that ;-) If someone could point me to the same info for Iford's GFS, I would appreciate.
I wouldn't bother with Canson, if only Ilford would be available here in my remote little place. The price difference is in disfavor of Ilford, after shipment.
EDIT: P-S: I should add, that as a selling point Ilford has got it's name as a big advantage. All my clients know the brand from the dark(room) ages. It has a traditional flavor.
Nino, I too have had some concern about the previous lack of corroborated information supporting the Archival properties of Ilford GFS, so I sent a request to them in Switzerland and got this reply:
<Gold Fibre Silk does contain a small amount of OBA in the paper fibres.
This explains the fluorescence you have reported. We do not believe this
quantity poses any risk to the archival properties of this material, as the
quantity is low. In addition, the fact that it is in the paper stock means
that it is not in the coated layer nor the baryta layer and is therefore
protected to some degree against yellowing. We have had enough confidence
in the archival properties of the product, to have submitted for Wilhelm
testing and for the Arttrust initiative and we believe the results to date
look very encouraging (see attached Press Release from Photokina 2010).>
In the press release they say that (as of then) the testing work was still underway. However, on my reading, the conclusive results were not ready then. I have checked Henry Wilhelm's site periodically, including just now, and not found any reports there yet, so either the work is on-going or arrangements to make it public are not yet in place.
Here in Toronto both the Canson and Ilford papers are now priced quite competitively - I'd use either depending on availability.