The Garett 340 in 44 mag seems to rule if your cylinder can handle it. Std S&W cylinders can only accommodate the Garett 310 gr load.
These are very hot loads intended for dangerous game - last ditch defense. There was a gunsmith who was altering Marlin rifles for the longer Garett 340 rds.
When I was younger I agonized over the decision whether to get double,or single action 44 mag. In my experience, second shot was so slow, due to recoil, that it didn't much matter.
Then I read about a Ranger who got attacked while releasing a bear. He had a single action and he didn't want to weaken his grip by cocking the piece one handed Too afraid he w lose it and then his life so he endured some abuse until he could cock w other hand and shoot the bear. he survived the attack.
Never forgot that story. Also, good reason to have a dummy cord JIC. I think Clark Custom has them for Super Blackhawks.