It mostly depends on the purpose.
Stereo audio means that the audio is mixed into two channels. So for example, one channel might play music louder, the other may play sound effects louder.
This allows for a more immersive experience, but at the same time requires the audio to be mixed for it by the game/emulator developers (otherwise it might as well be Mono).
In addition, if the speakers are located close together, it's much harder to notice the benefits as the sound will all be coming from the same general direction.