Deflation is not a viable strategy for a currency. It's bad because it makes hoarding a valuable strategy and hoarding reduce the amount of currency in circulation leading to even more deflation. Who wants to use a mean of exchange actually discouraging exchange ?

The alternative really is between low inflation and price stability. Government tends to prefer low inflation because it encourages people to invest their assets in a productive way and because it's actually pretty difficult to avoid any inflation via monetary policy.