You want to check the resolution of the scale, meaning the smallest increment the scale is capable of accurately reading. You want one with a resolution of at least. .1 grain. The cheaper ones will typically only go down to .2 grain. As an example, say you are trying to measure out 5.5 grains of powder. A scale with a .2 grain resolution will only give you readings of 5.2, 5.4, 5.6, 5.8, etc. A scale with .1 grain resolution will give readings of 5.2, 5.3, 5.4, 5.5, 5.6, etc. So with the .1 grain, you have a much better idea of where you are at. Thats the difference between the $75 dollar Brian Enos scale and the $47 Oldwillknot scale.
Spend more and you can get even better resolution, .05 grain and even .02 grain. With .05 grain resolution, then you would get readings of 5.40, 5.45, 5.50, 5.55, etc. However, usually as the resolution gets better, you may lose maximum capacity(the maximum amount of weight you can put on the scale)
That Hornady scale looks decent and has .1 grain resolution. This one from old will knot has a .05 grain resolution, but only has a capacity of a little over 300 grains, where as the Hornady can go up to 1500. But then again, 300 grains would be fine for measuring powder, but not if you were measuring larger bullets.
http://www.oldwillknottscales.com/je...le-jsvg20.html
Both the Hornady and the Brian Enos look good.