I have no experience hunting elk. Both the 270 and 308 have taken elk with no problems. Myself I would rather have the 308 for a elk hunt. You can shoot a bigger bullet and I would rather have it if I had to take a longer shot. Which being your sons only 14 and his first cow elk hunt you might not want him takeing longer shots. If you can you might have him shoot both rounds and see what he's more comfortable with.