A smoker is just that, a smoker. Thats what it does. Smokes constantly while slowly cooking the food.
A pellet grill is a grill that uses wood pellets to cook food, but has the ability to add smoke flavor.
Pellets can impart smoke flavor but will not do it as much as wood chips/chunks in a smoker.
A smoke tube will add more smoke flavor but maybe not equal an actual smoker.
These are just my thoughts on the differencs between the two.
