Don't bother with 10V ones, not even sure if they're easily found retail anymore. Usually the retail ones are 16V.

The voltage marked on a cap is the MAX operating voltage.

A 25V job will work identical to a 16V item if your operating voltage never exceeded 16V... but the 25V cap is usually dearer (by only a few cents) and may be physically larger.

The high-voltage ones like 250V or 400V are usually for mains filtering and are designed for AC voltage. Non-polarised caps are more expensive too.