I think the alpharag board is unbuffered. alphamount is buffered. both products use the microchamber papers, which is one of the best paper/board material on the market now. in the past, they usually recommend that you not use buffered materials with color photos (negs, slides, prints) or with certain older processes like cyanotypes, because the pH could cause color shifts & stains. for b&w though, you'd get more protection with a buffered, acid & lignin free paper/board--and these products both pass the PAT, so they're probably both okay. If I had a cyanotype or something, I'd probably use the rag board though. a guy I worked with once was from the smithsonian and his attitude was pretty much that when in doubt--go with the unbuffered.
hope this helps.