I like my Littman cardio IV. It’s never failed to pick up murmurs that you can’t hear (or can’t hear nearly as well) with other stethoscopes. I do zoo and it is still good for large animals sound-wise, but food animal/equine practitioners sometimes choose a longer tubing. That keeps your head a little farther away from the animal/allows you to listen through chutes more easily and can sacrifice the quality of the sound a bit, but is usually a bit safer.
In school, you probably don’t need to spend a ton on a stethoscope fwiw. They get stuffed in your bag and beat up. You can always ask your large animal clinicians what they use and go with that recommendation too.