Capacitance and voltage rating
Presuming that the capacitors are electrolytic, are in good working condition and their capacitance values are identical (since electrolytic capacitors have a tolerance range of -20% to +80%) they will test identically.

The working voltage of an electrolytic capacitor is the maximum voltage which should never be exceeded. At the same time, using a 300V electrolytic capacitor in a 10V circuit is not a good idea. In an electrolytic capacitor, the dielectric is an insulating oxide layer formed on its aluminium foil anode by electrolytic action when a  positive 'forming' voltage is applied to it. The working voltage is decided by the thickness of the oxide layer. During an electrolytic capacitors lifetime, the oxide layer would be maintained only if the working voltage is between 25% and 90% of the forming voltage. If not, the dielectric thickness would reduce leading to capacitor failure.