I did a lot of research before choosing a powder measure and had a lot of positive feedback on the uniflow so got a used one from ebay. it only came with the large cylinder.
Based on additional reading, I also purchased the baffle.
the first time I used it, I ran ~20 charges through it to get the powder metering evenly.
Every time I change a load, I run it till I get consistency, then run 5-10 charges through it watching/calculating each drop and average out the total on the scale to see how accurate the load is.
every time I charge, I do so with approx the same speed of the charge handle to ensure consistency. I have not tried doing charges at different speeds to see what negative affects this would cause.
With a large cylinder, and Win231/HP38 I can consistently get w/in .05gr +- of my intended charge.
Different powders will give different results. I have not tried my supply of unique through the measure due to referred difficulties in metering.