I'm a fan of the .284. I would say I have a cult following of the 7RM, however currently building or assembling parts for a 7SAUM. 7SAUM, 280AI are great cartridges that never really took off with the masses. (To be honest i dont really know much about the .280AI) Both have very similar ballistics, with the saum slightly better, if almsot negligible for most. For the hand loader and custom chamber crowd they have proven to be excellent performers. The 7PRC appears to be another great addition to the options of the .284. I look at it as the modern 7RM and for the non hand loader, a fantastic option. When the clicker issue gets figured out, it will be a true winner in my opinion, especially since there will be brass offerings from Peterson and ADG.
I wanted to build a "lighter weight" mountain rifle, but didn't want to sacrifice much performance, ie mid lengh AntiX action and carbon barrel, carbon stock. I decided to go with the SAUM because I like essentially easy cartridges that aren't know to be very temperamental, and have proven themselves on the F-class scene. And if im being honest here, probably its popularity. Its also on the moderate side of recoil, which maybe im a little b!@ch but i just dont enjoy rifles that hit hard and have difficulty observing bullet spalsh. I also have most of the components, bushings and mandrels for .284. I'm not a speed junky and try to choose one that will be moderate on barrels, but still be in the mid 2900s, so I can practice and not be as concerned about burning up a barrel. It's also said to be the big brother of the 6.5x47 Lapua, which is the last rifle I built. I plugged in some anticipated ballistics and it almost matched, which I'm hopeful for as it will make a great trainer.
The drawback of the 7SAUM is brass availability. I would secure enough brass to last the life of the barrel.