If you go the FEC route, get the 100. The 120 is great for a commercial setting. It has a convection fan that gives you fairly even top to bottom temps.
The 100 uses natural convection, so you need to think about the hot and cool spots in the cooker and which way the air is flowing when you place the meat - but having hotter and cooler areas gives you more flexibility for comp cooking. (chicken cooking, sauce setting, etc.)
So if you said you were opening a bbq restaurant, get the 120 or 240. For comp cooking, the 100.
Turns out a nice product, good smoke ring without resorting to Tender Quick. Does hot and fast just fine, but since the fire is so clean regardless of your cook temp, run it at a really low temp first (like 180 degrees for 90 minutes) to get more smoke on the meat.