On average the Win brass is harder and will last a little longer in teh primer pocket but if your loads are letting loose at 4 firings I would say your pressures are a bit high.
For a big game rifle I am generally not overly worried if I can get 4 shots per hull but in a comp or extreme range rifle I would prefer to get +6 firings.
While the Win brass is harder on average in the case head, it is also harder in the shoulder neck area. You may find that you will have to anneal your cases more often to prevent neck splits. I like to anneal every 5 firings but if your primers are getting sloppy at this point, no need to aneal.
Another point to remember, if your chamber is designed to use 8mm Rem Mag brass necked down, going with the 7mm STW brass necked up may create a looser neck fit.
As a general rule, if your throat is properly designed and dimensioned, this is not a major accuracy problem but it will work harden your brass more because it will stretch farther on firing and you will need to size it down more when sizing.
This may lead to earlier case neck splitting compared to the Rem brass.
If you have to turn your necks to fit the chamber, this point is moot!
Good Shooting!!!
Kirby Allen(50)