Centrally issued currencies such as the dollar, euro, yen, won, ruble are Inflationary. The central banks which issue these
currencies work to keep the inflation rate at around 2%, and typically have measures called Quantative Easing to manage the economy.
These inflationary measures can be a risk and provide instability.

We can't say that Bitcoin is more stable, its not and likely will never be. But we can say that as more and more people use bitcoin, there will be less and less bitcoin to go around, and Bitcoin will go up in value.

Thankfully, One Bitcoin is divisible up to 10-8, or 8 decimal points, as compared to only two decimal points of most traditional currencies.

Further, it will be fairly easy for the core developers to modify the bitcoin wallet software to be able to make bitcoins divisible up to 10-16 or more decimal points as adoption continues and bitcoin needs to be divided up even more.