If you are looking for the best fabric to make jeans, the sweetspot is at the midweights around 12-13oz.. any lighter can be suitable for womanswear and or wider fits.
heavy weight fabrics, 14oz and up are very suitable for jeans, but will be stiffer and need a longer break-in period. Heavy fabrics are also more durable for the obvious reasons.
Fabrics heavier than 17oz will be harder to wear and will not fade as nice, the tend to break quicker due to thicker folds at hips and inside knees.
The super heavy weights can be used perfect for bags