I shoot both. Here is my input:
.270 pros:
-Slightly flatter shooting. If you're not shooting much past 250 yards there is no practical difference.
-Will actually delivery more energy to the target past 250 yards. Doesn't suffer as much wind resistance so it retains it's velocity better at this range and therefore delivers more energy to the target.
30'06 Pros
-Delivers more energy to the target below 250 yards - AND - the larger diameter bullet will obviously create a larger wound channel.
-Can fire bullets which are a full 70grains larger than the .270 because of the larger bullet diameter making it often more suitable for larger game, especially close up.
-Much wider selection in bullets and factory loads available. This is a drastic difference.
Given the above facts, if I were to go hunting I would take the 30'06 every single time. I don't take shots greater than 250 yards. The 30'06 is superior for my use in both hitting power and ammunition/bullet selection. At under 250 yards there is a negligible difference in 'flatness of shooting'.
If your friend is doing 800 meter shooting at the range for kicks, then the .270 is probably well suited for him.