I seem to remember reading somewhere that most US tailors like the modern lightweight cloth, but most UK tailors don't (especially those on Savile Row).
Also, the weight of the wool is far from the only thing that determines how warm a garment is - a lightweight fabric that has a REALLY tight weave will be hotter than a heavy fabric with a looser weave, and the type of fabric also changes things - 12oz of linen and 12oz of wool are different beasts.
Also, the weight of the wool is far from the only thing that determines how warm a garment is - a lightweight fabric that has a REALLY tight weave will be hotter than a heavy fabric with a looser weave, and the type of fabric also changes things - 12oz of linen and 12oz of wool are different beasts.