There are only two popular types of mechanical powder measures. Just about all of them use a rotating drum …. ie Lyman 55, RCBS Uniflow, Hornady Lock-n-Load, Redding, etc. Of the rotating drum types, the Lyman 55 is the most accurate with most powders. It's baffle has a coarse, medium, and fine adjustments whereas most other measure have just one adjustment.
The other type of powder measure is a "slider" where the powder bar has an adjustable baffle and slides from the hopper to the drop tube. My Dillon RL550 has this type of powder measure and drops flake powders like Unique far more accurate than my Lyman 55 or Uniflow. These Dillon powder measures can also be used on any press with 7/8x14 threads.
Before you can compare different powder measures, you must test them with the same powders. Ball powders such as AA#5, W-231, H-110, etc drop very uniform from virtually all powder measures. Some powders are like dropping cockleburs …. like IMR 800X. I have never found a powder measure that drops extruded rifle powders accurately enough to suit me. The longer the powder pieces (looks like pencil leads) the worse they drop. I use my Uniflow in conjunction with a trickler and weigh each powder charge when using extruded rifle powders.
There's a lot to be said about "technique". When you develop a uniform movement for each powder drop, chances are the charge weight will be more uniform. The Lyman 55 has a nifty device that really helps. It is a "clanger" that taps the unit each time it is operated. This helps powder to settle in the baffle, thus a more uniform drop. Another trick that works is to keep the powder hopper at about the same fullness. I pour powder in the hopper until it is about half full. After each 100 rounds of handgun ammo, I'll top it off back to half full. With rifle loads, I do much the same except I top it off after 50 rounds.
In all honesty, there's really not much difference in drop accuracy between brands with a rotating drum. I would rate the Lyman 55 a little better than other brands because of the clanger and the three baffle adjustments. I would also rate the Dillon better for flake powders than any rotating drum type powder measures.