Well, if the 35 Rem Mag is the ballistic twin to the 35 Whelen, and is a shortened Win Mag case, and the WSMs are not just shortened but widened too, there should be some improvement over the Whelen.
I wonder, what 35 cal magnums are out there? I know only of the Norma Mag.
Another advantage of this is that if Winchester puts out this round, it means there will be rifles for it too. Not much selection in 35 Whelen. I wish the Rem Pumps were a standard item, not just a special one.