RE: 12ga. slug vs 30cal.
Provided they are both effectively accurate to 100 yards I honestly don't think the dead animal will ever know the differance. All of the cartridges you listed are more gun than will ever be needed to efficiently and effectively kill deer, elk or moose.
Remember that there are 12 ga shells that fire a 45 caliber rifle bullet (385 grain Nosler partition) at 2000 fps. This essentially duplicates a heavily loaded 45-70 or a 450 Marlins ballistics.