I buy by price. I have used shelves of Federals, Winchester, CCI, and soon will be using Magtech.
Bought Wolf, they were actually quite mild.
I agree with the statement that Federal are the "softest". A more accurate description would be "most sensitive", but hard and soft are concepts we have all experienced and are easily understood.
(Was that softball that hit my head "Hard", or just "insensitive"?
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Early on in my reloading life, when loading buffalo blasters in my 357's, I found that changing primers would create pressure problems. Federals were more mild and switching to Winchesters caused pierced primers and primer flow back into the the firing pin recess. And that was with the older, thicker cupped WSP.
I am into moderate loads now and primer changes are not that much of a problem.
If you are a coil cutter, if the firearm you have has a poorly designed ignition system with marginal firing pin strike, or your mainspring is worn out, then you will want to use the most sensitive primers you can find or you will have misfires.
I purchased a 586 from a friend who used it in PPC. It had under 100K rounds through it, might have been 40K, 60K, or 80K. He shot it a lot. Anyway he never had misfires because he was using Federal primers in his 38 Special cases. I was shooting 357 loads with AA#9, a ball powder, and WSP primers. WSP are normally great primers but it turned out not so good with a revolver with a weak mainspring, ball powder, and cold weather. I got squibs. Primer looked like it got wacked hard, but not hard enough.
I had to knock the bullet out of the throat with a screwdriver because I could not open the cylinder.
Incidentally, this has made me leery of ball powders. Ball powders are harder to ignite in cold weather.
Anyway a change to a new mainspring fixed all the ignition problems, and I was willing to trade off the wonderfully light double action pull (with the weak mainspring) for positive ignition in extreme conditions.
Others may be willing to live with an unreliable firearm as long as they are shooting under conditions where a malfunction only leads to a low score.