Not VS', but have been on BA's lots. It's a different concept from UA's, if I understand UA's correctly (just extra pitch?). Both BA and VS have different, wider seats as well, with fewer seats abreast in a row. VS PE has more extras thrown in than BA WT+, but both do have a few service tweaks that you don't get in Y. One of the good things about the BA cabin is unadvertised and unadvertisable: the cabin usually feels much calmer and a little bit more sophisticated than Y. But it's such a "soft" element that it's difficult to describe.