I have both cartridges.
.35 Whelen in a custom built Rem 700 rifle running 250gr Hornady Interlock.
.338-06 A-Square in a 17ā€ MOA Maximum Specialty Pistol running 200gr a win Ballistic Silvertip.

Both have their draw and place. Just depends on the need and situation. If I had to choose one cartridge regardless the platform, Iā€™d probably go .338-06 A-Square because of the larger bullet selection and slightly better external ballistics. But, I love the historical aspect of the Whelen.