The SHA carb is dead simple. You can't really adjust it's metering across the range of throttle positions. You just need to pray that the spray bar has the right size holes.
There is also no idle circuit adjustment. You just have one jet. And you get to try to get that ONE jet to cover all the operating reigiemes of your engnie.
It's not a good distuion.
The PHBG has a needle, which has progressive, and infinitely variable fueling across the throttle range. It also has a seperate pilot jet, which handles fueling at small throttle openings. And it has a main jet, which handles full throttle. And the needle jet which restricts the main jet to work well at part throttle settings.
The SHA is "easier" to tune, becuase there's less taht you can actually tune. The PHBG lets you tune everything. Which is a situation where you could have best power, good idle, and good fuel economy.