I own a couple-three of 'em. I find the stoney Point stuff gives more accurate and much more readily understood data.
I'm told its important to keep in mind that the numbers are RELATIVE, and not exact measurements.
If you can afford it, a good dial caliper and the Stoney Point gages are really nice, for about the cost of 2 of the RCBS dinguses you can measure any cartridge around...
Shoot carefully... swifter...