I suppose they can be accurate but I consider digital scales to be an example of "electronic" over-design because they introduce yet more things to go wrong, such as dead batteries or poor wiring connections. These and other possible pitfalls make the old mechanical scales look good to me.
I have found digital scales to be very reliable. Most are self-calibrating and the adaptability of them very convenient. In contrast the mechanical version is more difficulty to adjust in comparison. The only disadvantage is if the batteries or power source is not available. That is of course given they are not abused of course.
Normal ones are more accurate. .
A day in the morning and evening can the weight difference.