RAM 2500 - Hemi 6.4 vs Cummins - payload vs towing stability

I'd like to hear some reports of how the 6.4 tows heavy at serious elevations. I live at 1100' and routinely drive to and camp at elevations from 7000 to 9200 feet, and there is a lot of up and down before getting to 9000+ feet. I am impressed with the 6.4 Hemi, but would be curious how much power loss it experiences at those elevations. My Ram diesel of course is unaffected by the altitude.