Just curious as to why some people prefer to weigh the water rather than measure it with laboratory graduated cylinders. Seems like the "weighing" method is indirect and allows for more error (scale error; calibration error) while simply putting it in a graduated cylinder gives you a direct measurement. (I'm sure either method is fine for our purposes however.)
Yep. I still use cylinders. I think it's partly because my first degree was in science and although we used both for different reasons, I always tended to prefer cylinders. It's also for the same reason you mention - I would prefer to introduce one possible source of error rather than two, and to buy scales and calibration weights that I would be happy to trust would cost far more than to buy cylinders I am happy to trust. Also if you want to get slightly silly about it technically weighing only works for pure H2O. Obviously other liquids have different molecular weights.
Ultimately like you I do sometimes wonder if it really matters much - the amounts we're dosing are small and within a few weeks the doser will be mechanically different anyway. Same point re my molecular weights comment.