In my life as a USAF Metrologist, I repaired and calibrated both beam and digital scales and in fact we calibrated the check weights used to make sure the operator knew it was working correctly.
We had a 6 foot (2- 3 foot arms) bullion beam balance that was mounted inside a shock resistant glass case (with vertical sliding front) to remove any discrepancies from vibrations and air currents. It was accurate to +/- 0.000001 mg (1 microgram).
We would show it off when the Wing Commander would bring high ranking vistors to the Lab (Precision Measuring Equipment Laboratory). The Wing Commander knew the routine (because we pulled it on him
) We would give the visitor a piece of paper (which we knew the weight beforehand) and had him/her sigh it in pencil and then we would reweigh it. We would accurately weigh the amount of pencil lead and tell them the weight. The Wing Commander would then say to them, "I told you your signature didn't carry much weight" and then laugh. He loved bringing people in, especially if their signature was shorter than his as we had given him the paper that he signed and we annoted the weight of his signature.
Digital scales are good for quick, routine, repetative measurements but they do have their limitations (temperature, light (as mentioned before), vibrations, air currents). For the average reloader though, a decent digital, even the cheaper ones nowadays will do what you need and an efficient manner. Just use the check weight every now and then to make sure it's working like it's suppose to.