All the primos mouth calls work great. I have the Hot dog, Little dog, Ki-Yi and the Double whammy. These calls work great, takes some practice put you will get the hang of it. These calls are great especially for the money. If I were you go and get the Little dog and Ki-Yi.
The reason I say this is because it takes less are to breath into these calls, which makes it easier to use and get the hang of it. It's not extremely loud, it's more for your calm days, but more often then not it will work for what a coyote hunter needs
I would highly recommend getting an instructional DVD on how to use the primos hand calls. He will give a lot of pointers on how to pitch the call to sound combos and stuff like that.
Once you get the hang of the little dog and the Ki-Yi, if you still like the calls then go and get the Hot Dog. The Hot Dog takes a lot more air to make each sound. The Hot Dog is better once you get the hang of it and also the Hot dog is much louder than the Little dog.