I have factory restored B-77 that I use for recording. My deck is adjusted for the LPR35 from the factory but I had purchased after hearing it on a PR-99 machine. I did readjust the deck for the 90 and as you might expect, the 90 tape falls a little on the brighter side, but in my opinion falls short on the 77. In the end, it is important to consider what source you intend to record. Comparing the LPR90 to the LPR35 in playback, I prefer the 35 because to my ears, it records more evenly across the frequency spectrum. This was true for my Revox B-77 and very surprisingly for the (non-refurbished) PR-99. In conclusion, the LPR90 is a good tape and there is absolutely nothing wrong with it, but whatever technical (spec) advantages it offers, I can't hear compared to the LPR35 on my current tape decks. The LPR35 is also slightly less expensive so the helps.