Blinkmaster, the folks above who all answered part of your question, were mostly stuck on case longevity. That's all fine and dandy, but your main concern was "accuracy"
A few did comment on accuracy, but briefly.
There are some good reasons people gravitate to the time/field proven qualities of the 300 Winchester Magnum. However, if you're getting primer pockets loosening up after three reloadings, which happens, then there are other factors involved.
As often as not, magnum cartridges need to be load very close to maximum pressures to give the best accuracy/velocity combination.
Many folks just have to get another 50fps out of their rifle/cartridge combination, and focus on it over accuracy, this directly transfers to "short case life" no matter how soft or hard the case.
Granted, some cartridge cases have had their metallurgy tweaked to provide more strength and even better, more consistent weights. Lapua, Norma, Peterson, Federal Match, etc are some of the brands that have this quality.
The reason people gravitate to magnum cartridges isn't always a "good" reason and it comes back to bite them, as many just can't handle the recoil, even though they won't admit it. This limits how much they practice with the rifle/cartridge combination. Also you pay more for magnum cases/ammunition, which also puts limits on practice.
The original intent for using magnum cartridges was the ability to propel HEAVY bullets as fast as a standard cartridge propelled lighter bullets, and it still stands true for many shooters/hunters today.
However, new projectile designs such as Monometal bullets have changed the original parameters, so that velocities with these very strong, reduced weight bullets can be pushed much faster and still be consistently effective on game. Bonus.
There is a lot more to it than what has been written in this thread, by all who've responded, but IF ACCURACY is your main concern, mixed with acceptable velocity, then you will need to delve into other issues than the case and case life.
Case life is mostly determined by PRESSURE generated by your loads, and how you prepare your cases.
When you purchase Lapua/Norma/Nosler/etc cases, you aren't just getting "stronger" cases, you're getting a higher level of quality control, which minimizes inconsistencies such as case weight, metal distribution in critical areas, metallurgical consistency and the list goes on.
This contributes a lot towards "consistent" accuracy, but it's only the beginning.
I honestly don't worry about which cases are supposedly better, but I'm not shooting magnums either.
For the rifles I hunt with, I purchase at least 100 cases per lot, and weigh them for consistency, set aside those which are significantly lower or higher and use what's left for hunting. Usually I lose between 5-10 cases from a batch of 100.
I've got old Dominion cartridge cases for my 30-06 with well over 80 reloads, same for Gevelot 7x57 and 8x57. My reloads are all HOT, especially for the metric designations. The rifles I shoot them from are strong and I load them accordingly.
Right now, Lapua and other premium brands of cases are still available, but don't hold your breath for the price to come down any time soon.
The companies manufacturing them are gearing up for Western military resupply, if they haven't already, and that trumps civilian supply every time. You may just end up having to reload whatever is available. So, if you don't already, look at neck resizing only, rather than full length resizing every time for case longevity and optimal accuracy.
