I've been getting frustrated lately. I have been trying to sort my Lapua brass by weigt prior to priming/loading using my RCBS 5-0-5 balance beam scale, but have been getting inconsistent results. The exact same case can differ by as much as 0.2-0.3 gr upon a re-weigh. And it takes forever to weigh a case, waiting for the beam to settle down. Would I be better served by a digital scale? I think it would be quicker, but would it be more accurate and consistent?
I have both scales (Redding balance beam and an Ohaus Navigator Digital) and you should be able to get the same consistency/repeatability from both. The one statement that really bothers me in your original question is that you can reweigh the same case on your balance beam scale and you get a 2-3 tenths difference in weight. That is an real issue!
Double check the area around where the dampener is and make sure there isn't anything stuck to the magnet that would influence the raising and falling of the beam. I use 0000 steel wool to clean my necks and I have found times when 1 or 2 strands of the steel wool will find their way to this magnet. You will see an abnormal up/down pattern in the balance beam though when weighing. Also make sure there are no burrs on the fine edges of where the beam rotates. The fulcrum points. If there is a small burr or something there impeading the beam, it will give irratic readings also.
So check out your scale for problems first. There is something there. A balance beam works on simple physics. You should be able to weigh a case and be able to pull it off and replace it in the pan 10 times in a row and get the same reading. If not something mechanical is wrong your scale. One other thought is that if you have an A/C vent in your loading room, cut it off while weighing. Air flow will cause the beam to bounce also.
But to answer your simple question if the beam scale is working properly they both have the same accuracy, but the digital scale is faster for checking weights of components hands down. But it won't be more accurate.
If you do get a digital scale, be careful when using other electronic devices or flouresent lights around it. They can influence the electronics of the device with the magnetic fields. My gunsmith and I were talking and Dave was on his cordless phone while weighing charges on his digital scale. He kept saying, "something isn't right". Come to find out when he got to close to the scale with the cordless phone it would go haywire.
So check out your beam scale first because something is wrong there. If you still interested, the digital will work just as good but faster for repeat weighing of components. I always use my beam sclae to double check my electronic scale for a piece of mind.
Keep in mind I've never messed with the cheaper digital scales from the major reloading companies. I had heard good bad and indifferent stories about them. So I saved and spent the extra money for a good one. Not for the extra resolution it gives (.05 gr resolution) but the actual repeatability of the scale. My digital scale has always been on the money after it warms up. When I'm going to start weighing with it, I always plug it in about 1/2hr before use.