I suppose you mean to compare stability (of a currency's value) with deflationary development (of that currency's value). They do not really have anything to do with economic growth as such.

To answer the question, as I understand it, stability of a currency (in relation to the goods it buys)

- avoids continual change of prices of goods as expressed in a currency (think of having to change a price list frequently).

- simplifies comparative analysis of economic activity over time (think balance sheets).

- promotes public confidence in the currency.