I've never shot a moose but I doubt one would be any better than the other. The most important part is the bullet. That's a lot of animal but I understand easy to kill. In a 7mm mag I'd use at least a 160gr bullet better a 175 gr. In the 300 mag I've always felt the the best bullets were 200gr and up. I'm ssure there are people around shooting them with lighter bullets but I wouldn't care. Now if I did go moose hunting now, I'd take my 30-06 with 180gr bullets.
It is six one and a half of dozen of the other. They are both good. If it was me & that was the only 2 choices I would take the .300 because I like the 30 cal and am not overly fond of the 7 Mag. It will do the job quite nicely but I never did develope a liking for it.
In the spring of 2007 I was the unfortunate recipient of an injury cause by a damaged carbon arrow that shattered on release of the arrow. I was in the yard going to take a few practice shots before dinner and the second arrow is the one that did the damage. That day will forever be burned in my mind. After I release what happened I made mistake #2 I pulled the tail shaft of the arrow out of my hand causing more damage.
Thank goodness that my wife was home and was able to...