BigBuck,
To answer your question, no, I don't use the RCBS tool. I've used the Sinclair for some time now, and before that used one of the Lee hand primers. I haven't used the K&M but it lloks to be a very well designed and built tool. Not really the issue, as the method isn't nearly as important as some of the other considerations that go into this. Trying various brands and types of primers can make a huge difference in LR ammo, and is something that needs to be determined on target. Sorting primers by lot takes up a considerable amount of time for most serious Long Range shooters, as different lots can perform very differently. Makes a difference, and enough that the time is well spent to find a consistent lot. I don't shoot BR, but I do shoot LR prone, and this is something that's critical to us in that venue. I would think it'd be even more so for a BR shooter, given the more solid shooting platform.
Either way, getting primers seated properly isn't a major trick, and so long as it's done correctly, the other factors (such as those I mentioned) will make a much greater difference in the overall load and the accuracy on target.