There is a lot of good info here, and some poppycock too.
Yeah, yeah, Dells have a better transition. I'll take that Pepsi challenge any day. Period. Drive my car, then you'll understand that it ain't the carbs, it's the state of tune.
Gordo, I can clean an idle jet and be back down the road before you have your air cleaners off to get to yours. So I say big deal that they're on top.
I do agree with Stan that Synch is SUPER important. I do know my mileage went from 18 at pig-rich to a much improved 24-25 at lean-peak, no other adjustments. You spend a LOT of time with the throttle plate a few thousandths open from the idle stops when cruising, so in my opinion you are on the idle jets more than some people think. I know I no longer stink of raw gas after going for a drive like I used to. Also people behind me no longer have tears in their eyes.
Remember, the synch is only as good as the linkage. It's more important than you think. Either sync-link or good ball twist or hexbar with heim joints, without the heims you are whistling Dixie.....
I went from a .60 idle jet to a .575, not a big change but definitely a slightly leaner and more correct A/F ratio. .55 was too small and screwed the transition, gave me a flat spot.
I don't care which carbs you have, a clean fuel and air supply will keep them running just fine. Maybe the trouble with Webers is the numbers of carbs produced with an equally high number of non-knowledgeable mechanics which led to the fallacy that they suck. Who knows? All I know is it's been years since I've clogged a jet.