You're not going to get any argument from me. I did say, "7 SAUM is superior to everything IMO". But it is worth considering the huge improvement in efficiency of the 7x47, IF a 180 gr. Berger at 2750fps fills your needs. Consider this contrast, based on avg FPS reported for 26" barrels.
7SAUM - 63-65 grains - H1000/Retumbo - 180 gr - 2925fps
- DROP from 200 yds to 600 yds - 2.9", 10MPH wind @ 600 yds - 18.5"
7x47 - 43-44 grains - RL17/PP2000MR - 180 gr - 2750fps
- DROP from 200 yds to 600 yds - 3.3", 10MPH wind @ 600 yds - 20.4"
I think 7 SAUM is superior to anything in a short action for long range hunting. 284 case is too long requiring the 168,175 and 180 bearing surface to drop below the neck jct. If you use Lapua 6.5x284 brass, you may encounter donut issues after re-sizing. When those longer bullets have to be seated below the donut, those issues will be compounded. 7 SAUM can fit a 180 Berger at 2.98" OAL. For me it comes down to intended use. 7 SAUM for a pure hunting rifle. 284 only considered for 162 grains and lighter. 7x47 if I intend to shoot a higher volume for fun.