First,I've never shot anything bigger than an elk.
But over the course of several decades,I've never heard our Canadian brothers claim a .303 British inadequate for moose,and the 30-40 Krag has an honorable reputation on Moose.
A lot of those cartridges used older ,simple cup and core bullets. We have better today.
I can't say for sure,but it might be the 2400 fps or so vel did not cause over expansion and decreased penetration.
I have no doubt the 30-06 with a180 gr bullet is adequate,but not all 180 gr bullets offer the same expansion/penetration.
I would not choose a very "hard bullet,and I would not choose a soft,loose bullet.
Of course,there are other great bullets,but IMO,a Nosler Partition or Accubond are decent choices. I would have confidence in either,
20 more grains of lead will not make an earthshaking difference. That is 1/2 of the old standard 22 LR slug. That said,both theAccubond and the Partition areavailable in a 200 gr version.