Here are some PROS:
9x19mm is the most widely used centerfire pistol ammo in the world. (Which in times like these, can be a negative if buying ammo of the shelf.)
Generally, it costs about $6 less per 50rd box than .45acp ammo.
It is a high velocity, low recoil caliber and easy for most people to control.
The smaller case size allows for higher capacity than larger calibers in magazines of the same size.
Does not deliver the same stopping power as the .45 acp cartridge.
Full Metal Jacket ammo can over-penetrate target at close range.
In regards to your question about the Ruger, while I like a lot of their firearms that particular model does not really appeal to me. It is a well made pistol but I think there are other options in that size and price range that are a bit better options. The Kahr CW9 and Walther PPS come to mind.
Sic Semper Tyrannis