There are three main different styles of smokers: vertical, horizontal, and combination smokers.
Vertical--Also called water, or bullet smokers, a vertical smoker is designed in three layers: a heat pan on the bottom, water pan in the middle, and one or two grill grids the next layers up. A vertical smoker, starting at around $30, is an affordable way to go, particularly if you've never entered the world of smoking before. You can expect a vertical smoker of medium size to hold up to 50 pounds of meat at a time.
One of the drawbacks of the vertical smoker, however, is the lack of ventilation openings, and as such, these smokers must be tended to constantly and carefully. These smokers have a small door through which you can load fuel, and a lid. Using these two openings together, you can create an updraft, but learning to do so takes time and practice.
Despite that, vertical smokers remain a popular choice because the food layers help to baste each other from the top down. Rotating the grids the food is sitting on from bottom to top is suggested in order to baste and heat evenly, but doing so can be tricky to do.
If you decide to go with a vertical smoker, look into the models made by Brinkmann, Weber, and Charbroil as the better smokers will be found by these manufacturers.
Horizontal--The horizontal smoker, the one most used by championship barbeque teams, has a side firebox and a separate smoking chamber. These smokers begin at around $150 and go up to $2,000 for the best of the best of smokers designed for home use. If you are looking for a commercial grade horizontal smoker, perhaps even for the purpose of entering a barbeque competition yourself, then the price goes up even higher, depending upon what you are looking for, the capacity you need, and other factors.
Horizontal smokers cost more because a thicker type of steel is used. This is so the smoker will better retain heat, regulate temperature, and be a more efficient cooker altogether. Having the firebox on the side makes it easier to refill the fuel and also to maintain and manage the heat and smoke. In addition to this, if you wish you can also use the firebox in the function of a grill.
Combination Smokers--Just as it sounds, a combination smoker combines the side firebox of the horizontal smoker and the vertical smoking chamber, or it can also combine the side firebox with both horizontal and vertical smoking chambers. The models to look for here are Brinkman and New Braunfels, as they are the most likely to be found. They cater to both the home smoker as well as the professional