7mm mag vs 308 win is about 10 grains of bullet and 150 fps in favor of the 7 mag. Not enough any elk will feel a difference. The 308 gets it done with about 30 grains less powder. This is with a 175 grain bullet in the 7 mag and 165 grain bullet in the 308. BC is higher with the right bullets for the 7mm but shooting hunting bullets at hunting ranges I think that's a wash. I own and like both but what one can do so can the other.

As to taking a 50 cal elk hunting....I'm not going to say it will make your dick grow and inch....but I'm not going to say it won't either.