Nash at his peak was the better player. I think there's an argument that Hall may have had the "better career". Part of it comes down whether you value one of the "weakest" Hart wins over a Rocket Richard in a pretty tough field. Typically, i'd lean Hart > Rocket. But in this case, i think it's more debatable.
That's an interesting take. I generally think of Nash's Rocket Richard win (that he shared with Kovalchuk and Iginla) as a weak one. In fact, in that recent Rocket Richard winners tournament, I specifically called it weak.
I don't know... did he really beat great competition? Ovechkin and Stamkos weren't in the League yet, and he tied Iginla and Kovalchuk. A goal total of 41 also isn't that impressive, although '04 is one of the lowest scoring seasons of all-time.
In contrast, I think Hall's Hart win is quite solid. That season is definitely an outlier in his career, but even if you think he shouldn't have won the Hart, I do think it's better than any season Nash had. People rave about MacKinnon's 2018 season, but he only had four more assists than Hall (with the same number of goals) playing with better offensive players.
So I think Hall has the best single season between them (and maybe his best two or three seasons are better than Nash's best two or three), but Nash was more consistent in terms of productivity year-to-year during his prime and a better goal scorer. They both dropped off offensively at age 31.
Playoff play is a weak point for Nash, but Hall doesn't exactly have a legendary playoff career himself.