Wildhog,
There is no "one" most accuate, but that takes a bit of explaining. Expanding on Kevin's comments a bit, they all tend to do better with some types of powders, and not quite so well with others. This applies even to the top of the line benchrest measures like the Harrells. I bought one some years back, and took the time to run it against several other measure I had at the time. I ran hundred throw runs with several different types of powders, weighing each and every throw and averaging them for ES and SD. In the end, I found that the Harrell gave the best result with certian powders, and not nearly as well with some others. I ran it against a Redding BR-3 and a BR-30, as well as a Seely Masker converted Lyman, and got similar results with all of them; they each had their own bright spots, and others that they didn't show so well against the others. In addition, they also show preferences fro certian amounts of powder. In other words, they all seem to have a "sweet spot" of volume that they give their best results within. Go outside (above OR below)their sweet spot, and the ES and SDs tend to go up. I wound up sticking with the Redding BR-30 for most of my reloading, and selling off the others. For what I'm generally doing, that's the best combination for me. Not knocking the Harrells, and they're very well made.
Nothing wrong with thrown powder charges for shooting out to around 600 yards, but you'll find that most shooters competeing in LR matches use that as the dividing line between what we'll throw, and what we weigh out individually.