Samuel, it would depend on if you reload and if you need to shoot lead free ammunition. If you want something different and less recoil go with the 280 Ackley. If you don't reload and need to shoot lead free go with the 7mm mag. I live in Ca and I have to shoot lead free ammunition and only Nosler makes factor lead free ammunition in 280 Ackley. I just bought 2 280 Ackley. One is a Christensen Ridgeline in 280 Ackley and the other is a Begera premier 280 Ackley mountain rifle. They both shoot well. The Bergera action feels better but the Christensen looks cooler. Both have the same trigger. The Bergera is no longer carrying this rife since sales were so bad, this is what they told me when I called them about the mountain rifle in 280 Ackley. I have no experience with the 7mm mag so I can't tell you anything about that round. My other hunting rifle is a 300 Winchester Mag. Long story short about what caliber is better depending on ammunition if you ask me. The 7 mag is everywhere and the 280 Ackley is a boutique round.
Good luck with your rifle.
Jason