As far as *stunning* sounding mono goes, generally-speaking, Westminster Lp's of Chamber music can sound almost palpable. Surfaces can be noisy though. Orchestral music on Westminster or elsewhere...I can't say it's "about the sound." It's about performance: Currently, I'm a big fan of Scherchen's Beethoven. I'm also a big fan of Furtwangler.
So since I'm only familiar with Classical Mono, I could only say comfortably that most Chamber music on Westminster could be used for sound demonstrations, (but damn good performances too), and I'd only recommend going out of your way for large-scale Classical and/or Opera on mono when you've become tired of modern recordings of said performances, a lifetime's pursuit. I learned my Wagner through Nilsson, but only recently discovered Flagstad, who has Nilsson's clarion top but can also soften and feminize her voice as well. Now it's hard to go back to Nilsson, even though she's recorded better.
So you're probably asking a difficult question!
So since I'm only familiar with Classical Mono, I could only say comfortably that most Chamber music on Westminster could be used for sound demonstrations, (but damn good performances too), and I'd only recommend going out of your way for large-scale Classical and/or Opera on mono when you've become tired of modern recordings of said performances, a lifetime's pursuit. I learned my Wagner through Nilsson, but only recently discovered Flagstad, who has Nilsson's clarion top but can also soften and feminize her voice as well. Now it's hard to go back to Nilsson, even though she's recorded better.
So you're probably asking a difficult question!