I have hunted with grunt tubes for many years. On some occasions, I have had bucks come running right in looking for a fight,hair standing up on their backs and all,that is an exciting event. Early morning after a rain,near a fresh scrape,a grunt call will work better than you might think,and I am a believer!
I have also grunted from a stand, and thought nothing is coming, only to hear a deer get up from it's bed less than 100 yds away just before dark and come angling over to see who the other buck is in his neighborhood. I have jumped deer,grunted at them and had them stand there stamping their feet,trying to determine what I was. I use whatever I feel will give me an edge when hunting, and a grunt tube is usually on my lanyard when I'm deer hunting. I like grunt tubes that will play a single note too,using it almost like a turkey tube call. It can work as well as clucking to a turkey. I'm no expert,just sharing my observations,
Dave