Wide range of choice from the Hard Currencies.
To pick one from the above that suits own need.
Some prefer EUR, some might GBP, AUD etc (certainly not Russian Rouble, N/Korean Won).
In foreign exchange dynamics, when one major currency falls, others(in other economic region) often rise).
Strength of the money depends on the level of trust that issuing country gains from the outside world.
Factors: Trade and current account balance, political/social stability, unemployment rate, GDP-Debt ratio etc.
Even though it sometimes moves in the way defying economic fundamentals (by the influx of speculative fund).