If you have a think about it, the external dimensions of the cases should be very close as they are the same chambering (what is it?).
So a heavier case means thicker brass, hence less internal volume.
The same charge in a case of lower volume is going to produce more pressure, but conversely you can sometimes get the same muzzle velocity with less powder in a lower volume case.
1. How hard/soft is the brass. Not universal that you want really hard or really soft brass, it depends on application.
My .223 has quite a tight chamber, and I use a Lee Loader for it. Get away with using Norma .223 which sizes and seats bullets nicely. Very accurate!
On my .270, I run some very close to the limit loads with Barnes 110 TTSX (not recommended). So much so that during development I was waiting for the hottest possible day (about 26 degrees) in the area just to ensure my loads were not dangerous. Got some 'clickers' when extracting, ejector swipe marks and brass flow into the ejector (not good!)
Decided to change from the Winchester brass I was using to some Norma I had, problem solved. Admittedly I think the case capacity was a little higher in the Norma (hence lower pressure) but the case seemed to be springing back a little better and the primer pockets took multiple firings, whereas the Winchester was getting loose at two and toast at three.
2. How long do the primer pockets last (see above).
3. How much good brass can I get for cheap (or free!).
Brass prices have risen exponentially. Lapua .223 cases were under £60 a few years ago, now over £70!...
*WARNING!* Steep price hike on brass!
I am coming from the standpoint of a lazy reloader. I hate reloading but like accuracy, don't like wasting time at a loading bench or shooting loads over a chrono. You'll see a lot of comments about neck turning, primer pocket uniforming, neck mandrels and other minutiae, but I would challenge those who do this with their stalking ammo to do a blind comparison in accuracy with cases which had just been de-primed and full length sized (essentially one step).
