This is just speculation but I've heard that quite a few Whelen's have headspace issues because the shoulders are small. By increasing the shoulder angle you can give the case a clearer headspacing point. But that's not from experience, just an educated guess.
The alleged case life improvement Graybeard mentions is also another advantage, if it really does make a difference.
It certainly isn't the beasts that the .257 Roberts AI, .280 Rem AI, 7x57AI or even the 30-06 AI are but as Graybeard says, you have to decide.