Now that's a good comparison. Most times people compare the 9mm to the 40 S&W or to the 45 ACP.
Assuming you can have only one, I'll go with the .357 Mag revolver. Very effective for self defense, powerful enough for hunting, capable of shooting .38 Special for practice and plinking, inherently accurate with its fixed barrel, reliable, and only needs an additional trigger pull in the event of a misfire.
The advantage of the .45 ACP 1911 is that it is faster shooting and faster to reload, and the 45 ACP cartridge delivers a large bullet that doesn't need to rely on expansion. Perhaps a better fighting handgun, but not nearly as versatile as the .357 Mag.