Availability is king, and familiarity is queen. I've primarily used CCI for 35 years, as they were available when I started. I've used a couple K of WLR when CCI wasn't available, and many 1000s of S&B for service rifle when they were cheap at Cabellas. Stayed away from Fed due to the packaging size, and never tried REM. Only problems I've ever had were seating the WW in PPU brass, I'm more inclined to blame that on the brass. I should get some Fed SP just for my S&W Model 624-3 as it tends towards light strikes since it got a new Wolf trigger spring sometime in the 90s.