I once wrote software that automatically graded wine "sweetness" based on sugar grams/L output via Spectroscopy? (I think) in a lab. After learing which wines regions / varietals produced what rating (sweet / dry / extra dry) is pretty much all I need now when picking wine. I'd say the sweetness is probably the only major difference between varietals but maybe it's just me. Extra dry is what I like best.
I believe white is generally higher sugar but there are drier white wines still. There was a model fit to sugar content and it worked across red white and rose.
