A diameter of .454 vs. .429 is not essentially the same.
And the .45 Auto can certainly be used with JHP, or SWC just as the .44 can. There may be reliability issues, but the .45 can be throated to improve that.
However, the .44 Special can do some things the .45 just cannot do, for example, it can be loaded to close to .44 Magnum power.