Which Thermometer is best for dairy products?

I am trying to make cheese/yogurt and I can borrow a thermometer (to save money). However its a candy/deep fry thermometer (goes from 80F to 400F much higher than I will need for dairy). There are two options; a “mercury” thermometer that is in a protective glass casing or a metal one with a “gage”. Both have a clip to attach it to the side of a pot. I was curious on which is the better one to borrow. Pros and Cons.