I have both the Primos original estrous doe can and the Primos fawn bleat. Both work at times. I called in a buck, spooked him when my stand sqeaked, then called him back in, and killed him. That one was sighted first. I've called in several bucks with it that I sighted first but for one reason or another never took or had a shot.
I've had less success blind calling with either the can or a grunt tube. I've rattled in several bucks, but none that were mature enough to shoot.
The fawn bleat seems to work better with does. It must arouse their maternal instincts. The problem with it is they come in jumpy because they are looking for a fawn in distress, I guess. Sometimes they ignore it, but I have watched does ignore real fawns bleating like crazy. I think once they are trying to ditch the fawns, the fawn bleat is no longer effective. If you are looking to score on a doe early in the season, they will work better. It sometimes gets the attention of the bucks during the prerut faze. I guess they think a doe is trying to dump the fawns, so she can breed. They will come in less jumpy than the does because they are looking for something different. I haven't managed to get a mature buck in this way yet, but I wouldn't discount it at the right time of the year.
Any call will work sometimes, but none of them work every time. I certainly wouldn't abandon a call because it failed once or twice. Timing can be very important.