I own both the 300 Win Mag and 338 Win Mag. They are both very good long range guns. If I had to chose one it would be the 300 Win Mag just because bullet and ammo are easier and cheaper to find. I used one on 2 trips to Africa and it killed everything with ease....I was not hunting elephant, hippo or cape buffalo.
I'll add you can easily find ammo in RSA if the luggage gets lost