For the Blue Smoke Smoker, he only offers one size, 24x48, but honestly I wouldn't go smaller than a 24 x 48 for a backyard offset anyways. You have to remember you're going to have a hot spot on the firebox side, and with a 24x48 you get about 36-40 inches of actual usable cooking space. With that in mind I would think a 24x36 is going to be a little cramped, but that's just my opinion, and it's about what YOU want.
On the upper rack, it's an add on priced at $150.00 for the Blue Smoke Smoker. If you want the extra guage, that's another $50, and the stack damper (mandatory IMO) is $100. So $300 for all the extras puts it at $2,000 even and it's close enough you could pick it up rather than having it shipped which will save you a lot of money. The Bell Fab needs to be shipped to you from Oklahoma... which is going to make it more expensive.
I’ll take the contrary position. I have had electric, pellet, competition quality charcoal cabinet and my Lang. I love the Lang and haven’t used the others for almost two years now. That said I still have my charcoal cabinet as if the need ever arises off overnight cooks it runs all night on a load of coal. Someone mentioned wood too. The one thing I underestimated when I bought the Lang was how much wood I’d need. Took me the first year to find sensibly priced wood sources. Make sure you have that.
You're in the Dallas/Fort Worth area? You should definitely check out Big Phil's Smokers offshoot brand Blue Smoke Smokers. He's located in Caddo Mills Texas, which is right in your area.
His Blue Smoke Smoker brand offers what seems like the best bang for the buck for a back yard offset... it's a 24x48 cook chamber with a 24x24 round fire box. The Pipe used for both the cook chamber and the fire box are 3/8" thick steel, while the end caps, collector and stack are 1/4" steel. The base model includes a single grate, and single Tell True guage for $1,700.00, which is right in your budget. It has a huge 6" wide 42" long stack. He also offers all kinds of add on's at very reasonable prices. If nothing else I would HIGHLY recommend you get the stack damper added as that is not standard, but it's a $100 add on. That's all you need.
Bell Fab is nice too, but Big Phil's/Blue Smoke Smokers is much closer to you. Another thing to consider is how you like your heat and smoke to flow. Think about cooking a brisket or a pork butt... do you prefer fat cap up, or fat cap down? If you like fat cap up you want a traditional open pit design that cooks from the top down. If you like fat cap down you want a bottom up cooker. Big Phil's Blue Smoke Smoker is a traditional open pit design (meaning no baffle, no tuning plates) and is a top down cooker. I understand Bell Fab's are Bottom up cookers as that is Craig the owner's preference. Both are good, which is better is based on your own personal preference.
I'm firmly in the top down cooker camp, as I like to cook fat cap up. I have a Blue Smoke Smoker and couldn't be more happy with it. I'd buy it again in a heart beat. Mine was a lot more expensive, but that's because I added just about every possible option, but it was still only $2,600 even with all those options. The pit draws like a freight train, and keeping a screaming hot coal bed is super easy. I also love the way it renders fat... the huge stack causes a ton of airflow and convection which just renders fat in an incredible way, much different and much better than any other pit I own, including a reverse flow stick burner I have.
I checked out the two refurbished/enhanced used smokers this afternoon. I decided to get one of them. It is built like a tank and in excellent condition. 18"x 36" with a rectangular reinforced fire box stack with damper, solid steel table, iron rear wheels and casters on the front and a temp gauge. It has one main cooking grate and a smaller upper cooking grate. It also has a drain plug with control valve and an ash rake. My buddy who is an experienced offset smoker guy thought it was a really good smoker that would meet my needs. I'm psyched!!!