Re: RCBS, Redding Powder dispensers??
Redding, RCBS, Lyman, Hornady, all very good for ball powders...any effective differences are trival and variations between individual tools, not the brand.
I prefer the Redding and Hornady measures because they come standard with a nicely calibrated adjustment knob for resettng the cavity easily.
Do get a bench stand. Then set it back a foot or more from the bench front edge and near the press.
Putting a measure on the front eats valuable bench space unnessarily, exposes the measure itself to stray bumps and possible damage as well as making it inconvient to use! Only worst place to put a measure is in the press!
Lee's little plastic "Perfect" measure is perhaps the best, most consistant, device to meter coarse grained rifle powders but it's not so good with ball powders.
Anything works as well as another for medium grained powders.