If you have a choice, 4 Ohms is a harder load for all amplifiers and as a result they make more distortion driving such a load. So if the speaker could be made to be 8 or 16 Ohms without otherwise changing it, it would sound smoother and more detailed because the amp driving it would make less distortion. Distortion obscures detail and usually adds to harshness and brightness.
If the speaker were 95dB instead of 89dB you would need 1/4th the amplifier power to make the same sound pressure. Also worth noting!- if the speaker is rated 4 Ohms and 89dB, to translate to efficiency rather than sensitivity (efficiency is 1 Watt at 1 meter, while sensitivity is 2.83 Volts at one meter; so if 8 Ohms both are the same but at 4 Ohms they are not!), it turns out that the 4 Ohm speaker has an efficiency rating of only 86dB!
If you want the best sound, its a good idea to not have the amplifier work hard for a living!