I have been using SU carbs on my Range Rover that were installed on my 110 when purchased, I agree that tuning them is a bit difficult but with a proper air suction meter the calibration is less stressful.
These carbs need to have all their seals in perfect condition otherwise it will be impossible to tune them.
On the performance issue they are very responsive, they don't have the flooding problem because of their design. My advise is to fill their domes with AT oil during summer time and engine oil in winter time to get a better acceleration.
They are so good that whenever I find one for sale I automatically buy it.

