It’s funny, most physicians agree that the cheap disposable stethoscopes in isolation rooms are the best, mostly because they are so loud it’s difficult miss anything with them. However, I am not a cardiologist so they may have a different opinion.
I've actually found them pretty terrible. I can't hear subtle findings at all with those. My usual stethoscope is an older-model Littman Cardiology III with stiff rubber and a dual pediatric-adult head. I've had it for over 25 years.
I would really disagree as a physician that's used a lot of random crap stethoscopes when I don't have one or in an iso room. Those disposable ones are different in what they pick up, some findings are louder others not detectable. Sure I can pick up some stuff like rubs and systolic murmurs but you aren't going to get more subtle findings like diastolic murmurs and fine crackles. Probably a combination of certain frequencies responding and also me being used to mine.