When the voltage was unified in UE, the nominal value was set to the median of 230 V, but its tolerance was raised from 10% to 15%, so that the new maximum peak value of 230V + 15% will match the old value of 240 V + 10%.
So now for all 220/230/240 V standards you have the same maximum voltage value that is used for electrical designs (about 265 V effective), so they are equivalent, regardless of the name.
True, however there is also old equipment. For example I have heard that light bulbs designed for 220V will last for noticeably shorter period of time ar 230V nominal circuit. That is why it is worth to check supported voltage. But you are right - newer equipment will suport all voltages.