"..... I took a 338 and 458 Win. Mags for some plains game and buffalo. I am really torn between the 300 and the 338..... One or the other."

I agree, I have a '63 M70 in 300Win (pure stock, except for glass bedding/tuned trigger/3-9 Leupold) that will put 3 under an inch at 100yds all day long (with it's favorite handload). Perfect for typical north American hunting, but for African use, I think the extra power (bullet weight/penitration) of the 338 makes it a preferable light/med rifle. Now, that's not to say a hunter with a 300 made a poor choice, or is defenseless.