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Originally Posted by GMB
I should just point out that reducing the size of the capacitor does NOT reduce the inrush current at all, probably increases it I suspect.
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OK, strictly speaking the instantaneous initial inrush current will be zero, assuming there is some inductance in the circuit. The current at the next instant depends on circuit resistance, inductance and capacitance. When we say 'inrush current' we probably mean the current averaged over some appropriate initial time period, which may relate to switch bounce time.
The damage done to a switch by a current surge is likely to depend on both the size of the surge and the length in time of the surge. A smaller cap means a shorter surge. Any blue spark is not caused by the switch closing but opening, possibly due to switch bounce during what we call closing. A capacitor will help prevent this by limiting the maximum voltage (Vmax = sqrt(L/C) x current broken).