The bigger the jumps, the more important it is to be able to accurately ride to the correct distance. For a pro who is always right, the mechanical difference of riding 2’6” vs 3’6” are minimal. It’s just more hang time.
The more difficult to quantify, but perhaps better metric to work from would be how much of your horses scope you’re using at a particular height. If you’re jumping Dobbin around 3ft, and his maximum physical potential is 3’3”, you better be damn accurate. Dobbin just doesn’t have it in the tank to save you if you get him to the oxer on the half stride. But say you’re riding Thunde, who could easily tool around four and a half feet. If you’re jumping a 3ft course and you get him to a funny spot, he’s got the scope and athleticism to take the flyer or get out if his own way if you burry him.
The biggest thing about crossing into the meter’s is that it’s almost never a school horse that’ll take you there. If they can stay sound jumping 3ft+ and take school horse level jokes and bad rides they’re too valuable to be teaching lessons on.