Cameron, the 35 Whelan improved is a great cartridge and very little difference between that and the 338-06 or the 9.3x62. I would keep the 338-06 as the last rifle "they" would let me keep because I can easily make 338-06 ammo from 30-06 and plentiful 338 bullets. Not so with the 9.3x62 or 6.5MS. I have always favoured slow fat bullets of good construction for humane kills on game deer size and up. I did originally defend 300 Mags on this site as woods cartridges as the devil's advocate, mainly due to hack writers in gun magazines, which I no longer buy, telling me I can't use a 300 Whoppenstomper Magnum in the woods, oh, really. FWIW I inadvertently shredded the front end of a small deer when it stepped back as I pulled the trigger on a 243 Win. Too fast, cheap bullet, a Sierra boatail. A Barnes or Nosler partition bullet would have not done that damage, so it's all down to the bullet, use cheap ones for practice, use premium bullets for the hunt.
Mike
