I built a 280 AI for 1,000 yard F-class and was impressed with its accuracy and ease of finding accurate nodes. I shot my best 200 yard 5 shot group I have ever shot under a half inch, I only shoot groups when initial sorting out loads. I took the load that shot hat great 200 yards and jumped directly out to 1,000 and was very happy with the results.
The 280 AI I built was not the SAAMI round but the traditional load based off of the 30-06 case, this was before ADG and Peterson started to make brass and I would not build a comp gun that did not start out with Lapua brass. One other benefit going for the original cartridge is it has a little more case capacity than the SAAMI case. But the difference in case capacity is probably not enough to make a noticeable difference. Go with the SAAMI case if you want to buy ammo off the shelf or are worried about resale. Go with the original if you want to use Lapua brass as the parent, fireforming is trivial as you run the 30-06 in the sizer and it reduces the upper portion of the neck leaving the reast of the neck at the 308 diameter which gives you a false shoulder. I turned the necks prior to resizing so I could turn to just below the neck into the shoulder redcuing the chance of the dreaded donut.
For hunting purposes the animals would probably not notice any difference between the 7 RM and the 280 AI at ranges under 700-800 yards. I would have to look at the ballistics tables to get a better idea of the range where the difference in energy would make a difference between the two, so like anything else you read on the internet do the research yourself if those are the ranges you are interested in attaining while hunting. For target practice I do not think steel or paper would ever notice the difference between the two 7 mm cartridges.
Isn't great to have so many choices available to us in terms of cartridges, actions, brass, barrels, etc. that we did not have even 10 years ago.
wade