if a webber is set up right it'll run sweet. likewise if the pierburg is setup right it will also run sweet! its a myth that a webber will give you more power and/or economy than a properly working 2e2. However a webber is much easier to tune to take advantage of any performance mods you carry out, plus any rolling road you take it too is much more likely to be able to re-jet it and fiddle without messing it up!
My old 1.6 had just about every fault possible with the 2e2, but once I fixed them all it ran just as smooth as any of my GTIs I've had since, and fuel economy was out of this world, especially paired up with the 4+e gearbox.
The bottom line is if the basic unit has not been fiddled with then its easy to diagnose and fix any problems. If some backstreet mechanic has messed with the flaps and levers to try to 'fix' a problem then it needs a lot more head scratching, the hayes carb manual is needed here as it takes you through all the procedures required to reset all the complex inner workings back to spec.