Well, due to the extreme differences in ballistic coefficient, the 300 Win mag is carrying about an additional 900 ftlbs energy at 300yds.
In real world though, I don't think there is an animal you would hunt with one that you would not hunt with the other.
Nothing at all wrong with the Whelen. Used to have one in a Rem 7600. Great shooter. I would look more at the 225gr range though for better down range performance....even though a 200gr Hornady spitzer will do everything you need it to.
