I have had a very successful hunting career and in my 33 years of hunting, I have managed to take 200 Whitetail deer.

I have shot every round from the .22 short to the big 375 H&H in my lifetime at paper targets. So I have a pretty fair baseline of knowing ballistics and firepower in the woods.

In all my attempts to shoot whitetails, I have only kicked myself in the butt about missing a deer - maybe 10 times. Out of those 10 times, 5 of those times were due to the optics and not because I was under-gunned.

The one and only time I was under gunned, it was with a .35 Remington and the deer was 300 yards away and Buck Fever took over and my mind was not working like it should. If I would have aimed dead center on the deer on every shot, there was a pretty good chance that I would have hit it sooner or later.

If I would have had more shells and not just the 5 rounds I took with me that day, I would have kept shooting till the buck was down.

If the property next to where I was hunting was not posted, I would have kept after that deer until I got it.

If my aunt would have had a schlong, she would have been my Uncle.

On opening day of rifle season - anywhere for whitetails, I can usually be found carrying a Remington Gamemaster 30-06 or .270

After the opening day of rifle season, I can usually be found carrying a .300 Winchester magnum - if I know that I will be hunting in a open area where long shots presents itself. Or my .270 WSM.
I have a gun for when it is raining, I have a gun for when I am hunting in the open, I have a gun for hunting where it is close up and personal, I have a gun for long shots..

When firepower is in the front of my mind, the '06 and 270 can't be beat. When accuracy is key - the '06 and 270 can't be beat.
But if I want to make sure that if I hit it, it will go down and I won't have to track it or fight with another hunter over who shot it and would it have died if they didn't shoot it after I shot it, the magnum is the way to go.

I only bought the .300 Winchester in case I ever got the chance to go Elk hunting and not because I thought that it was a better gun then the Remington when it came to hunting deer anywhere on the eastern side of the USA!
Maybe it would be a better round for bears.
Most times when you hunt bears, the bear is really close and you have a split second to shoot or not shoot. A 30-30 with open sights is probably a better gun for that situation.

As far as reloading a Magnum for pennies more then the 30-06, I will call you out on that one.

To reload, first you have to buy the die's. Then you have to have the empty shells, then you have to buy Magnum primers. Then you have to have more powder for each round.
The bullets are exactly the same between my 30-06 and a .300 Winchester Magnum, but the factory loads cost twice as much.

Let's say IMR 4350 powder is about $24 a can, for a one pound can.
Let's say, as a example that you can get 100 rounds of '06 shells out of a 1 pound can, depending on how you load the shell.
We can use 58 Grains as a example.

When I move up to a .300 Winchester Magnum, it might take as much as 75 Grains of powder to reload just one shell. Every time I reload (3) - 300 WM - I could have reloaded (4) 30-06's.