The dispensers don't buy you anything thast I can see. Any quality measure will throw charges close enough that even a benchrest rifle won't notice the difference.
If you mean that a good volumetric powder measure throws charges as accurately as an electronic powder dispenser, then I'd disagree. The accuracy of a volumetric powder dispenser is very dependent on the shape of the powder grains, and the best powders for larger calibers tend to dispense poorly in volumetric powder dispensers.
Most of my pre-purchase research was reading the reviews at Midway, and a little bit of YouTubage and forum crawling for opinions and insight. I bought the RCBS Chargemaster 1500 and I'm VERY pleased with it.
I crank out .223 semi-auto plinking ammo on my Lee LoadMaster progressive press using a volumetric powder drop, although with all of the case prep needed for rifle cases, only the powder drop, bullet seating and crimping are done progressively. I do the case prep on the RCBS Case Prep Center that I modified to do all case prep functions after resizing... including trimming. I have a couple of YouTube videos if you're interested. I use only powders that meter well for the progressive powder measure and I visually inspect each. One of the MANY advantages of the RCBS ChargeMaster powder dispenser is the accurate measurement BY WEIGHT of almost any powder. It's essentially a powder dribbler on steroids.
For loading anything less than the 220 grains of powder I use in .50 BMG, the RCBS ChargeMaster has dispensed another accurate powder load while I seated the bullet over the previously dispensed powder charge, and I don't wait long for .50 BMG - just long enough to verify OAL before crimping. For volume production of accurate hand loaded rifle ammo, the ChargeMaster is a big time saver. It does all the powder measuring while I'm doing other things.
The ChargeMaster is also great for load development. No fussy powder bushings or powder volume to weight translation charts or powder dribblers. I punch in 22.0 grains and automatically dispense five charges of powder. Then I punch in 22.2 grains and dispense five more, and so on, throughout my powder load test range. Easy as pie. I like pie!
I wouldn't by a powder dispenser if you want to progressively load pistol ammo of one recipe out of a load book, but for accurate rifle ammo, it's a real time saver. Yes, you can do the same thing with a powder drop onto a scale and trickle powder manually to the desired weight, but you'll need a powder drop, scale and powder dribbler... and a lot more time.
If you want to reload .50 BMG, be sure to check the capacity of the other dispensers, and their dispensing speed. A large part of my decision to get the ChargeMaster a few years ago was the capacity and speed that were compatible with reloading .50 BMG without making two powder drops. At the time, the others weren't practical. The RCBS got higher marks on build quality and reliability back then too, and from my experience, that reputation is warranted. It seemed to be worth the small increase in price compared to other brands.
Finally, if you're put off by the high cost and you're looking to justify it, you're getting a great digital scale as part of the ChargeMaster automatic powder dispenser, and you can easily use that scale as a standalone digital scale for all your reloading needs.
