A currency board is a harder commitment than an ordinary currency-peg because it removes the discretion. The board issues domestic money only against inflows of the anchor currency and redeems on demand at the fixed rate, so the money supply rises and falls with the balance of payments rather than with a policy decision.
The credibility gain is real: interest rates converge toward the anchor economy's and inflation usually follows. The cost is that the domestic economy absorbs shocks through employment and prices instead of through the exchange rate, since there is no rate to adjust.
Hong Kong's arrangement against the US dollar and Bulgaria's lev against the euro at 1.95583 are long-running examples. Argentina's convertibility regime of the 1990s is the standard example of one abandoned under pressure.
Example: under a board, $1 billion of net inflows creates exactly $1 billion equivalent of domestic money. If the inflow reverses, domestic money contracts by the same amount whatever the local economy needs.
Related: currency-peg, dollarization, capital-controls, balance-of-payments