RE: Still trying to decide...
You could pick any of the three & end up with a great gun either way. The only help I might be to you is reminding you about ammo cost?
The 270-Winchester will be the cheapest & most avalible ammo.
The 270-WSM is the "new & sexy" round on the block. The sales have been strong, so the 270-WSM is here to stay. The ammo for the 270-WSM is about $10.00 a box more that the standard 270-winchester around here.
The 280 is another fine choice. The 280 is a 7mm caliber bullet. The ammo for the 280 sells for about the same price as the 270-winchester. I really do not think there is any advantage to the 280 unless you reload? Even if you reload the advantage would be marginal. If you bought the 280 & had a gunsmith ream it out to 280-A.I. then you would have an advantage.
Good luck in making your choice.