First off, good luck on that draw, you will need it
Second, if you are going to use a patched round ball on Moose in a state where you will be one EXTREMELY lucky guy to get drawn, I personally would use the rifle I was most accurate with and could deliver the most lead to target. Either the .54 or the .58 can deliver the weight needed to drop a good bull efficiently so you just need to figure which one you are the absolutely MOST accurate with. It would be a rare thing to get a longer shot than 75 yards in the Main swamps and woods so your range will be fine.