308 win
your your just splitting hairs with those to picks, up side to the /06 is only about 100fps where with the 308win the up side is lighter ammo in your pockeks , lighter gun on your shoulder when walking around, shorter gun for the brush, less felt recoil , less muzzle blast, and short actions tend to be stiffer (less flex)= more accurate , so lets see ..... that 6 too 1 for the 308win
the 400 yard shot hummmm......... leave both at home , unless it is sighted in for that , but then you just might shoot over a 150yard shot, my limit is 400 yards with my 7mmWSM or my 270win's , and 300 yards max with my 308win , 300 to 350 yards with my 7mm-08, 100 too 150 , with my 35rem's, 32rem and 75 to 100 with my 44 mag rifles's
if your set on a 30cal and set on a 400 yard shot you should look at a magnum cal , 300WSM , 300win Mag. 300H&H,