You talking 7mm STW, 7mm Weatherby mag, 7mm RUM, 7mm RSAUM, 7mm Dakota, or 7mm WSM?
Why does everyone keep saying "7 mag" - there is no such chambering.
But the answer to the question doesn't change - the .280 remington is the probably the best all-around north american big-game cartridge, followed closely by .30-'06 then closely again by .270 win. .280 is an improved .270 (better bullets) doesn't get any better for most uses. But .30-'06 is never a mistake. Don't get a .30 cal maggie - most people shoot them a few times, then sell them at a loss to get something lower recoiling and cheaper to feed -there's a reason for this phenomenon.
In my view, if your game needs something bigger than .30-'06, a .300 maggie ain't gonna help. If you need range, a 7mm or .270 caliber round will get there with less drop and drift. If you need more bullet (very large game / body weight), it's time to step up to .338-'06, .35 Whelen, 9.3x62mm, .45-70 govt, or .375 HH mag.
Don't get a Weatherby chambering - unless you have a enjoy spending unnecessary money and a sore shoulder. And .300 win mag? It's not a horrible round like some, but it's still an unneeded belted round.