So what are the whizbang magic features? Wouldn't more pathways be a negative in long term use?
If you think about it, they are the last carbs you would ever need to buy and long as you have the tuning parts. Why? Well Let's say you have an internally stock cb750 engine running a perfectly tuned set of webers, and you decide you want to go to 836cc, port your head, and run a high lift, high duration cam. Instead of buying new carbs to accommodate the increase in intake flow capacity, you would just change the venturi sleve (on webers they are sometimes called the choke but they aren't like a cold start choke). For a 40 sized weber carb body, you can vary the venturi anywhere from 24-36mm. Think about it, that's like being able to turn your stock PD 28mm carbs into 36mm carbs to feed your overbored over cammed engine without having to buy another rack.
Impressed yet?
the other thing is that they have 1 jet feeding multiple circuits, and the size of the venturi helps meter the fuel through the vacuum pulled through it. So think about it - you could increase the venturi size 1 size over the optimal street size and push the power band top heavy. You'll make more power but it will all be upper RPM range - great if you are running a big open banked high speed track like Daytona where you will spend most of your time almost at redline, or you can go one size under optimal street size and push the power band more to the torque-y bottom end of the spectrum to run a short tight road course. And it takes something like 30 minutes total to do the change over. By playing with jet and venturi sizes you can come up with a combination for nearly any engine in almost any terrestrial atmospheric condition.
Finally I think Weber DCOEs only have 3 moving parts, and almost all tuning and adjustments can be done with the carb installed on the engine.
Don't get me wrong, modern Fuel Injection is still better than any carb, but when it comes to the old mechanical tool that is a carburetor Webers are king.
