Lot of measures will throw accurate charges. Advantage to Harrell's is the ability to dial in precise throws using the micrometer adjustment. I calibrate mine at home and log settings in a measure book carried with the measure in its box. Throw accurate charges anywhere without weighing. Other advantage is its a fine piece of work smooth and precise. 

My Belding and Mull throws accurate too. Have to set the charge with a depth micrometer, otherwise it's trial and error scale checking getting the drops right. Use it for Black Powder only. It will throw stick powders fine just a pain to set. 

Difference in the two night and day, and they both throw precise charges. 

Boats