Have owned a .280rem and several .270s. The problem with the .280 is long bullets are too long for optimum seating. They work; but you will achieve better results from a shorter case, all things being equal.
Of course, you don't/can't utilize all the capacity of a .280 or any .30-06 derivative, except maybe a Whelen. So, the .284 shines for longrange where you need usable capacity.
A 175gr Sierra BTSP in 7mm measures 1.415" oal. Don't have any .277 bullets anymore, but a 130gr sierra BTSP loaded round measures 3.275" oal from my old ammo stash. DWM case and bullet seated length of neck; not protruding below shoulder. If seated the same on a necked up .270win case (which describes the .280rem, no?) the oal is about 3.575" oal which could be problem in some rifles. There are many even longer bullets out there for 7mm.
About the only downside of the .284 I could imagine is reduced magazine capacity due to case diameter, but as I can load almost 6rds into a win70 la magazine, the difference of .027 per case is negligible.
Look at the case dimensions of ctgs with reputation for most innate precision, PPC, BR, .308 variants etc and all are short-bodied. The .338 Norma will likely supersede the Lapua.
A long action enables the .284 win to make best use of its longrange potential and shoot the long oal bullets that have highest ballistic coefficiency.
