Ateam: I have Hunted with both a 280 Remington and a 7mm Remington Magnum for a LONG time now.
I have killt Bull Elk, Mule Deer, Antelope, Whitetailed Deer, Mt. Goat and Black Bear with bo'fum (urban youth word for "both of them"!)!
Properly placed projectiles (through the heart/lungs!) from either cartridge WILL harvest your game!
In fact I owned a Ruger heavy barrel Model 77-V in caliber 7mm Remington Express starting back in 1982. The 7mm Remington Express was simply the 280 Remington with a "fancy monicker"!
That 77-V in 7mm Remington Express (280 Remington) was an Antelope and high plains Mule Deer killing MACHINE!
I wish I had never sold that one.
Then in 1986 I had a full custom Rifle built for myself in caliber 280 Remington.
It was built on a pre-64 Winchester Model 70 action (that was "born" the same month and year as I was - July 1947!) with a 25" Douglas barrel and a McMillan stock - this Rifle is one of the safest, most reliable, most accurate and handsome Rifles I have ever owned!
And at about the same time I purchased a Remington 700 Classic in caliber 7mm Remington Magnum. It was a whimsical kind of a good deal purchase but that Rifle shot so well that it has been in my Hunting Rifle arsenal for 24 very successful years now.
I shoot 160 grain Nosler Partitions out of my 7mm Remington Magnum and 140 grain Nosler Partitions out of my 280 Remington.
Seldom do I ever fire more than ONE shot at a game animal with either Rifle!!!
Indeed the 7mm Remington Magnum has slightly more energy and a slightly flatter trajectory than the 280 Remington but I would not consider either cartridge to be lacking in any way when it comes to Big Game Hunting.
IF, you are considering one over the other and Montana Elk Hunting is in your future then I would tend to direct you to the wonderful 7mm Remington Magnum cartridge for that - along with the SUPERB 160 grain Nosler Partitions. Then I would suggest you have another loading tested and ready for your Pennsylvania Hunting - for this I would use either the 140 grain Nosler Partions or the 140 grain Nosler Ballistic Tips.
Best of luck to ya with whichever you choose.
Hold into the wind
VarmintGuy