I haven't seen Sound Inside yet but I thought Betrayal was one of the best Pinter productions ever (and one of his more accessible stories). Of course I love Pinter and Tom Hiddleston. That helps.
IMO The Sound Inside is an incredible work that pulls you in And never lets go. It it profound and enjoyable. Betrayal is a good production of an okay play. So early in the season, but Aound Inside and it’s two cast members will be serious candidates for Tony Awards. I don’t see that happening for Betrayal...maybe Best Revival nominee if it is not a strong season for revivals.