I'd opt for 280ai if I was doing a custom build and if it was not for the fact that I have a stockpile of 7wsm factory ammo and components.
I have a 7mm rem mag, 280ai and 7wsm all with nominal unsuppressed barrel lengths and they are factory rifles so typical factory twist rates.
The 280ai is the most accurate and the 7rm is 3/4 MOA at 100y with almost any 160-168 grain factory ammo I feed it. I'm not messing with changing either.
The 7wsm was woefully inaccurate. However, a friend of mine sold off his 7wsm rifles around the time I acquired mine and I got a lot of ammo and brass so I'm not worried about components (although I too would like to have the option of Lapua, Peterson, ADG, etc. better brass).
Recently, I swapped the original pretty laminate stock with a Win70 Coyote stock. Now it is definitely sub-moa, even with the factory 160AB ammo that was 3-5moa with the old stock. So now I need to test what I have but still seems like the best option for a shorter suppressor ready option given what I already have to work with. Possibly I will chop it and/or swap it to a shorter barrel.
If I go the route of a custom build for that need, the 7saum and 280ai will be on the list. I do like the latter because personally I like to see both components as well as factory ammo options for any new platform I invest in.