Comparing the mature animals, a moose is thicker across the body than an elk. Therefore, more to penetrate before hitting the vitals. This would be particularly true for any shot at an angle.
In the past, the 30-caliber 220-grain bullet was regarded as the ideal for moose, for the '06. I think that with the R&D on bullets during these last ten or fifteen years, penetration now with a quality 180-grain bullet is probably as good as with the old 220s.
You're from BATFE? Come right in! I use all your fine products!