Sounds like you have a gun dealer who' s trying to push you towards big boomers for little or no reason. Don' t even worry about the 7mm-08 ' dropping like a rock.' Now, the .270 probably shoots a little flatter, and if he' s pushing power, the short mags make sense. Seriously, I would look at the calibers he' s talking about like this:

7mm-08 is a beautiful shooting, light kicking, deerslayer. I would buy one and never look back. It' s as or more accurate as/than any other caliber I' ve ever seen.

The .270 is just as good as the 7mm-08, kicks a little more, and shoots a little flatter. Also, it is a much more popular (available/cheaper) caliber. I would trust mine with my life.

The short mags would provide you something to shoot elk and the like with, if you were forced to use the same gun.

If you' re not concerned about buying another rifle later on, the only reason you' d steer away from the 7mm-08 is to save money on ammo. I wouldn' t even hesitate if I were in your position.