This really is a Dodge vs Chevy, Remington vs Winchester, Bud vs Miller argument.
I have BWS and had the privilege of cooking on a SW this past weekend actually. Either are very good, well made cookers.
I can get a good 5-7 hour burn in my cooker using just the vents and without any charcoal pan mods. I dont have a removable water pan but would recommend getting one.
I like the BW for the mobility it offers, I can easily move it myself on wheels or using a handtruck. Hard to do that with the heavier SW
I didn't like the shelves on the SW, or at least the way they came apart. I also don't know if the heavier material is needed in the shelves. That being said, I don't think you may ever have to replace them. The BWS uses a lighter oven type shelf that I have yet to max out or have a problem with.
The thing I don't like about the BWS is the ergonomics. It is set up so the door swings open to the right making it perfect if you are a lefty but kind of a PIA for us right handed people. I bought mine used, so I am not sure if you can order the door on the other side, but I have never seen one.
I know that these seem like small chit things but I think thats all you can find wrong with either of these fine units.
"What sort of people are these charcoal masters? They behaved badly and were unconcerned with appearances. Their hair was long and unkempt and their clothes were wrinkled and old. They drank beer to and from the crab house and they made rude noises while we cooked." Tao of Charcoal