I do not think it is possible to generalize. I have heard a few high efficiency speakers: Lowther, Tannoy, Avantgarde, and Zu. And I have heard a few low efficiency speakers as well.
In general, low efficiency speakers have a brutal kind of sound. These are typically very linear sounding, with ample bass. The sound from these speakers are typically very impressive. But as we all know, impressive does not necessarily mean they are musical.
The high efficiency speakers I have heard, without exception, suffered from problems. The Tannoys have a lazy coloration that kills the rhythm of music. The Zu's sound distant and uninvolving. The Avantgardes have horn coloration. The Lowthers are beautiful, but lack treble and bass extension. (Yes, I know this is a gross generalization but it is based on the systems I have heard).
Of all the high efficiency speakers I have heard, the Lowthers impressed me the most. But that is my particular musical taste (classical). YMMV.
In general, low efficiency speakers have a brutal kind of sound. These are typically very linear sounding, with ample bass. The sound from these speakers are typically very impressive. But as we all know, impressive does not necessarily mean they are musical.
The high efficiency speakers I have heard, without exception, suffered from problems. The Tannoys have a lazy coloration that kills the rhythm of music. The Zu's sound distant and uninvolving. The Avantgardes have horn coloration. The Lowthers are beautiful, but lack treble and bass extension. (Yes, I know this is a gross generalization but it is based on the systems I have heard).
Of all the high efficiency speakers I have heard, the Lowthers impressed me the most. But that is my particular musical taste (classical). YMMV.