Why would you get a Rum over a Roy?
Can you spell COMPENSATION?
I do not need as much compensation as some but more than others. That is why my 7mm is an STW.
in the heavier bullets (175gr) the Roy matches the Rum in speed with the exact same powder but ~14grs less powder.
Seriously, the 7 Wea has almost the exact same case capacity as the 7 Rem. And loaded to equivalent pressures, there is zero performance differences. So the question might be: "Why buy a 7 Wea instead of a 7 Rem mag?"
But the Ultra mag case has considerable more capacity and does allow more velocity from the round. But at the cost of more powder usage, recoil, muzzle blast, and throat erosion. Each of us has to draw the line somewhere, at how much velocity we need vs how much of the aforementioned costs we are willing to pay.
Some think the 7 Mauser give the perfect ratio of power vs cost, others like the 280 Rem, while others are prepared to pay the cost associated with the 7 mm REm or Wea mag.
I draw the line at the STW. I like the velocity it delivers with 160 gr bullets, But I can not enjoy shooting anything which kicks me harder than the STW does.