One thing to watch out for with the Dellorto carbs is that they are not made anymore. Parts can be a real bear to find depending on what you need. Webers are still in production (who knows for how long) so parts are easier to get. The only reason I can think that the webers would clog less is that they changed to tall jet stacks in later years. This way the intake to the jets was up inside the aircleaner instead of level with the base. This would allow large particles to settle out into
the bottom of the air cleaner and not be sucked into the jets. I don't know if Dellorto ever did this or not.
hope this helps,
Craig
the Gorge VW club
gorgevwclub.com
ps - I am not a carb guru. This is just from my limited experience.